JESSICA M. SCOTT1, WHITNEY E. HORNSBY2, AMY LANE2, AARTI A. KENJALE2, NEIL D. EVES3, and LEE W. JONES4 1 Universities Space Research Association, Houston, TX; 2Duke University Medical Center, Durham, NC; 3Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, CANADA; and 4Cardiology Service, Department of Medicine, Memorial Sloan Kettering Cancer Center, New York, NY
ABSTRACT SCOTT, J. M., W. E. HORNSBY, A. LANE, A. A. KENJALE, N. D. EVES, and L. W. JONES. Reliability of Maximal Cardiopulmonary Exercise Testing in Men with Prostate Cancer. Med. Sci. Sports Exerc., Vol. 47, No. 1, pp. 27–32, 2015. Purpose: To accurately assess exercise interventions and to evaluate acute and chronic cardiovascular effects in patients with early-stage cancer, consistently reliable functional outcome measures must be obtained. An incremental cardiopulmonary exercise test (CPET) with gas exchange ˙ O2peak) provides the gold standard outcome of cardiorespiratory fitness. Methods: In measurement to assess peak oxygen consumption (V the context of a randomized controlled trial, 40 patients with prostate cancer (mean age, 59 T 7 yr) after radical prostatectomy performed two maximal CPET within 5.6 T 5.5 d of each other. Incremental treadmill tests were performed in the morning under identical laboratory conditions. Reliability and within-subject variability from test 1 to test 2 for peak and submaximal variables were assessed by correlation coefficients, intraclass correlations (ICC), Bland–Altman plots, coefficient of variation, and paired t-tests. Results: There was high ˙ O2peak (r = 0.92; P G 0.001; ICC, 0.900), ventilatory threshold (r = 0.88; P G 0.001; ICC, 0.927), minute reliability between CPET for V ˙ E/V ˙ CO2) (r = 0.86; P G 0.001; ICC, 0.850), and peak heart rate (r = 0.95; P G 0.001; ventilation–carbon dioxide production relation (V ICC, 0.944). However, high within-subject variability was observed for all CPET parameters (mean coefficient of variation, 4.7%). ˙ O2peak (27.0 T 5.6 vs 28.1 T 5.3 mLIkgj1Iminj1, Compared with those for test 1, significantly higher mean values were observed for V ˙ E/V ˙ CO2 (31.3 T 5.8 vs 32.8 T 3.4, P G 0.05) in test 2. P G 0.05), ventilatory threshold (1.91 T 0.5 vs 1.97 T 0.4 LIminj1, P G 0.05), and V Conclusions: These findings indicate the presence of significant, and potentially clinically important, variability in CPET procedures in men with clinically localized prostate cancer and have important implications for the application and use of CPET to evaluate the efficacy of interventions to improve aerobic capacity in the oncology setting. Key Words: TEST REPRODUCIBILITY, PROSTATE CANCER, ONCOLOGY, CARDIOVASCULAR FITNESS
P
have proposed that aerobic-based exercise training may improve cardiorespiratory fitness and cardiovascular risk profiles in patients with PC (18,23). However, to accurately assess exercise interventions and evaluate acute and chronic cardiovascular late effects in patients with an early-stage disease, consistently reliable functional outcome measures must be obtained. Over the past half decade, noninvasive cardiopulmonary exercise testing (CPET) has emerged as a research and clinical tool of immense value given its ability to accurately ˙ O2peak) (which, in turn, can be evaluate aerobic capacity (V used for risk stratification or evaluation of intervention efficacy), to assess the principal determinants of exercise intolerance, and to develop individualized aerobic training prescriptions (14,16,17). Importantly, the within-patient variability of CPET variables in PC has not been ascertained. Consequently, establishing repeatability of CPET in PC is critical not only to ensure accurate assessment of changes in cardiorespiratory fitness across interventions but also to precisely characterize acute and chronic cardiovascular effects for risk stratification. Accordingly, as a prespecified substudy of a randomized trial investigating the efficacy of aerobic training in men with clinically localized ˙ O2peak PC after RP, we evaluated the reproducibility of V
rostate cancer (PC) is the most common non-skin cancer diagnosis among North American men (1). Radical prostatectomy (RP), a primary treatment for early-stage localized PC, is associated with 10-yr survival rates of approximately 90% (1,24). However, RP’s side effects include urinary incontinence, erectile dysfunction, pain, and reduced physical functioning (6). Collectively, these side effects negatively affect health-related quality of life for up to 12 months after surgery (9). Despite significant advances in pharmacotherapy, continuing development of new interventions to improve health-related quality of life remains a high priority for this patient population (22). We, and others,
Address for correspondence: Lee W. Jones, Ph.D., Cardiology Service, Department of Medicine, Memorial Sloan Kettering Cancer Center, New York, NY 10065; E-mail: [email protected]. Submitted for publication March 2014. Accepted for publication April 2014. 0195-9131/15/4701-0027/0 MEDICINE & SCIENCE IN SPORTS & EXERCISEÒ Copyright Ó 2014 by the American College of Sports Medicine DOI: 10.1249/MSS.0000000000000370
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Reliability of Maximal Cardiopulmonary Exercise Testing in Men with Prostate Cancer
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and other important CPET parameters to assess the need for repeat testing.
METHODS Patient cohort, setting, and procedures. This is a secondary analysis of baseline data obtained in the context of a randomized trial investigating the efficacy of aerobic training in men with clinically localized PC after RP. The full details of the study methods have been reported previously (18). In brief, the major eligibility criteria were as follows: 1) e4 months from RP to study enrollment, 2) no absolute contraindications to a maximal CPET, 3) willingness to travel to Duke University Medical Center, 4) primary attending urologist’s ˙ O2peak (mLIkgj1Iminj1) below that of ageapproval, and 5) V matched sedentary normative values (18). All study procedures were reviewed and approved by the Duke University Medical Center institutional review boards. All subjects signed a written consent before the initiation of any study-related procedures. After the initial eligibility determination, all patients performed a maximal CPET as part of the study’s screening procedures (visit 1). If no CPET-related adverse events were detected, all patients returned to perform a repeat CPET (visit 2). Maximal CPET procedures. All CPET were performed using an incremental treadmill test (modified Balke protocol) on a motorized treadmill with 12-lead ECG monitoring (MacÒ 5000; GE Healthcare). Participants were provided with detailed, standardized, verbal instructions before each test and were told to avoid exercise, caffeine, and alcohol for 24 h and consume medications as usual. All testing was performed between 8:00 and 10:00 a.m. Complete calibration of gas concentrations using primary standard gases and flow using a 3-L syringe were performed before each test. All tests were performed by the same two certified exercise physiologists. To avoid bias, testers intentionally did not view the results of test 1 immediately before conducting test 2. Before beginning the test, subjects were familiarized with the mouthpiece and walking on the treadmill for approximately 10 min, followed by 10 min of rest. After stable resting metabolic values were achieved (including blood pressure and HR), subjects began walking at a pace selected in the warm-up as a comfortable but brisk pace (approximately 2.5–4.0 mph) at 0% grade for 2 min. During the test, participants were encouraged to walk for as long as possible, resulting in a peak, symptom-limited, exhaustive effort. Grade was increased every 2 min until ventilatory threshold (VT) (determined independently in each test) and then every minute thereafter until exhaustion or a symptom limitation (15). RPE were evaluated at the end of each workload using the modified Borg scale. Whether patients gave a maximal effort was determined on the basis of a combination of symptoms (dyspnea on exertion and/or fatigue as primary end points) and physiological measures (defined as a plateau in oxygen consumption during the final stage, HRmax 9 85% of age-adjusted predicted HRmax, and RER 9 1.10) (10). Metabolic gas exchange was measured continuously during exercise and averaged over 30-s intervals (Parvo Medics ˙ O2peak was TrueOneÒ 2400; Parvo Medics, Sandy, UT). V
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˙ O2 value for a given 30-s interval within defined as the highest V ˙ O2 at VT was independently the last 60 s of exercise. The V determined by a blinded reader using standard methods (2,26). ˙ E/ The minute ventilation–carbon dioxide production relation (V ˙ CO2 slope) was determined by measuring the slope across the V entire duration of the test (3). Statistical analyses. Means are expressed using either TSD or 10th and 90th percentiles. Within-subject variability from test 1 to test 2 was evaluated by within-subject absolute change (i.e., either an increase or decrease from test 1 to test 2) and tested using paired samples t-tests. Bland–Altman plots were constructed, defined as the difference in values from test 2 and test 1 plotted versus the average of the values from tests 1 and 2 with SD of the difference (average difference T 1.96 SD of the difference) (7). Reliability of the CPET outcome measures was assessed by Pearson correlations and intraclass correlations (ICC). One-sided 95% confidence intervals (CI) of Pearson correlations were made using the Fisher z transformation. For each variable, the coefficient of variation (CV) was defined as follows: (withinsubject SD/within-subject mean) 100%. Significance for all tests was set at P G 0.05.
RESULTS Participant characteristics. Details regarding response rates and profiles of the participants have been reported previously (18). In brief, 50 patients were randomized in the parent trial and 40 (80%) successfully completed two baseline CPET (2) (Table 1). Participant recruitment TABLE 1. Participant characteristics (n = 40). Variable
Overall (n = 40)
Age (yr) Weight (kg) Body mass index (kgImj2) Race, n (%) White Black Asian Current smoker, n (%) Comorbid conditions, n (%) Hypertension Hyperlipidemia Diabetes mellitus CAD Pulmonary disease None of these comorbid conditions Tumor characteristics PSA PSA category, n (%) G4 4–10.0 10.1–19.9 20.0–49.9 Gleason sum, n (%) G7 Q7 Type of surgery, n (%) Robotic Radical Days from postsurgery to randomization
60 (7) 87.6 (12.8) 28.0 (3.3) 27 11 2 1
(68) (28) (5) (3)
24 22 6 3 12 7
(60) (55) (15) (8) (30) (18)
6.2 (4.2) 7 30 2 1
(18) (75) (5) (3)
18 (45) 22 (55) 15 (38) 25 (63) 74 (38)
Values are expressed as n (%). PSA, Prostate-specific antigen.
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TABLE 2. Reliability of CPET. Test 1 11.3 27.0 2.39 161 31.3 1.91 1.18
T T T T T T T
2.2 5.6 0.5 17 5.8 0.4 0.08
Test 2
R
One-sided 95% CI
ICC
P Value
T T T T T T T
0.750 0.919 0.943 0.949 0.864 0.957 0.670
0.541 0.861 0.856 0.945 0.851 0.790 0.440
0.927 0.900 0.927 0.938 0.864 0.873 0.927
G0.001 G0.001 G0.001 G0.001 G0.001 G0.001 G0.001
11.5 28.1 2.49 163 32.8 1.97 1.19
2.2 5.3 0.5 16 3.4 0.4 0.07
P value corresponds to the R value.
took place between November 2009 and July 2012. The two baseline CPET were separated by 5.6 T 5.5 d. No serious or lifethreatening adverse events were observed during any CPET procedures. During baseline CPET, ischemic ECG changes (Q2.0-mm ST depression) were observed in three patients. Test–retest reliability. Pearson correlations and ICC for peak and submaximal variables are summarized in Table 2. There was a significant correlation between the two tests, with ˙ O2peak, HR), 0.96 correlation coefficients of 0.94 (absolute V (VT), and 0.67 (RER). ICC ranged from 0.927 (absolute ˙ O2peak, RER, exercise time), 0.790 (VT), and 0.938 (HR). V Within-subject test–retest variability. Test–retest variability (CV) for peak and submaximal parameters ranged from ˙ O2peak), and up to 2.2% (HR), 4.2% (indexed and absolute V 7.6% (exercise duration). Exercise duration (11.3 T 2.2 vs 11.5 T ˙ O2peak (2.39 T 0.5 vs 2.49 T 0.5 LIminj1; 27.0 T 5.6 2.2 min), V vs 28.1 T 5.3 mLIkgj1Iminj1; P G 0.01), peak HR (161 T 17 vs 163 T 16 bpm), VT (1.91 T 0.4 vs 1.97 T 0.4 LIminj1), and ˙ E/V ˙ CO2 (32.1 T 5.8 vs 32.8 T 3.4) increased from test 1 to V test 2 (Table 3). The percentage of subjects who increased on test 2 was greater than the percentage of those who decreased ˙ O2peak (72%), exercise time (75%), HR (68%), V ˙ E/ for V ˙ CO2 (83%), and VT (65%). As shown in Figure 1A and B, V there was a high variability between tests for peak variables (95% CI of 25.2–29.8 mLIkgj1Iminj1, 2.2–2.7 LIminj1 ˙ O2peak), and 155–167 bpm (HR)) and submaximal vari(V ˙ E/V ˙ CO2), ables (Fig. 2A and B) (95% CI of 31.0–33.8 (V 1.72–2.09 LIminj1 (VT)). Variability was similar for subjects ˙ O2peak (Figs. 1 and 2). with lower versus those with higher V
DISCUSSION The principal finding of this ancillary analysis was that despite the good test–retest CPET reliability, there was a significant within-subject variability in peak and submaximal variables (CV ranging from 2% to 8%) in men with
localized PC. Accordingly, we contend that our data suggest the need to perform two CPET at baseline to obtain valid ˙ O2peak and other CPET results in men after RP for baseline V clinically localized PC. Such variability has critical impli˙ O2 data, cations for the acquisition of accurate baseline V which, in turn, could affect prognosis and risk stratification ˙ O2 in and the magnitude of intervention efficacy to change V patients with cancer. Some studies have closely examined the variability of measurements obtained during CPET in other clinical populations with conflicting results. In the ‘‘Heart Failure: A Controlled Trial Investigating Outcomes of Exercise TraiNing ˙ O2peak was not different in (HF-ACTION)’’ trial, the mean V test 1 and 2 (15.2 T 5.0 vs 15.2 T 5.0 mLIkgj1Iminj1, P = 0.78) (5). However, there was a large within-subject variability ˙ O2peak, which the authors attributed to variations (6.6%) for V in subject factors specific to patients with heart failure such as daily hemodynamic and volume status fluctuations. A more recent investigation involving patients with heart failure with ˙ O2peak preserved ejection fraction reported no difference in V between tests 1 and 2 (14.4 vs 14.3 mLIkgj1Iminj1), with authors concluding that the incremental gain in information should be balanced by the increase in participant burden and cost (25). In contrast, current CPET guidelines in clinical populations with cardiovascular and respiratory disease recommend that at least two CPET be conducted in all clinical and research settings; these recommendations were formulated on the basis of previous work demonstrating that ˙ O2peak significantly varies over serial tests (2,12). For examV ple, Elborn et al. (8) performed three consecutive treadmillbased CPET separated by 2 wk in 30 subjects with heart ˙ O2peak improved significantly from failure. The mean V the first to the second test (14.1 vs 14.9 mLIkgj1Iminj1, P G 0.005), with no difference between tests 2 and 3 whereas the average within-subject CV was 6%. These find˙ O2peak ings are consistent with those observed here, in which V increased significantly from 27.0 to 28.1 mLIkgj1Iminj1 and
TABLE 3. Test–retest variability of CPET variables. Test 1 Exercise time (min) Indexed oxygen uptake (mLIkgj1Iminj1) Absolute oxygen uptake (LIminj1) HR (bpm) VT (LIminj1) Ventilation per carbon dioxide slope RER
11.3 27.0 2.39 161 1.91 32.1 1.18
(9.0, 15.0) (20.9, 33.7) (1.86, 2.97) (146, 187) (1.37, 2.29) (29.1, 37.1) (1.11, 1.31)
Test 2 11.5 28.1 2.49 163 1.97 32.8 1.19
(9, 14.5) (22.3, 34.9) (1.92, 3.03) (146, 184) (1.43, 2.45) (29.0, 37.3) (1.11, 1.32)
P Value
Absolute Change (2 – 1)
%291
%192
CV (%)
0.35 0.003 0.001 0.14 0.01 0.02 0.14
0.23 1.1 0.10 2 0.07 0.65 0.01
75 72 72 68 65 83 65
25 28 28 32 35 17 35
7.6 4.2 4.2 2.2 7.5 2.9 3.1
Values are expressed as mean (10th percentile, 90th percentile) unless noted otherwise. P value corresponds to a paired t-test of the null hypothesis that the mean of test 2 j the mean of test 1 = 0.
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Exercise time (min) Indexed peak oxygen uptake (mLIkgj1Iminj1) Absolute peak oxygen uptake (LIminj1) HR (bpm) Ventilation per carbon dioxide slope Oxygen uptake at VT (LIminj1) RER
CLINICAL SCIENCES ˙ O2peak (A) and FIGURE 1—Bland–Altman plot for peak variables: V peak HR (B).
the within-subject CV was 4.2%. In addition, the percentage of subjects who increased on test 2 (72%) was greater than the percentage of those who decreased (28%). Submaximal re˙ E/V ˙ CO2 slope have been used with sponses such as VT and V greater frequency to classify exercise intolerance and to riskstratify in clinical populations (5,25). In contrast to previous investigations on patients with heart failure reporting nearly identical mean values on tests 1 and 2 for submaximal indices (5,25), here, we found that 83% (33/40) and 65% ˙ E/V ˙ CO2 slope and VT, re(26/40) of subjects increased V spectively, on test 2. Taken together, these findings are indicative of variability in men with localized PC. We did not conduct a third CPET; however, on the basis of previous literature, an additional test is unlikely to provide clinically relevant changes (8,13,21). The variability in both maximal and submaximal CPET parameters observed in the present study is potentially clinically meaningful. For example, there is growing evi˙ O2 for both prognostic (14,20) dence supporting the use of V and risk stratification (4,27) purposes in numerous oncology clinical scenarios. These findings underscore the significance of accurate CPET-derived peak and submaximal measures, particularly given the increasing number of cancer diagnoses combined with the large and rapidly growing number of cancer survivors who could benefit from a global measure of the integrative capacity of the pulmonary, cardiovascular, and skeletal muscle systems to deliver and use O2. Furthermore, in the parent trial, we found that mean
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˙ O2peak increased from 28.1 mLIkgj1Iminj1 at baseline (as V recorded in the second CPET) to 30.1 mLIkgj1Iminj1 at week 24, an increase of 9% among patients randomized to supervised aerobic training. There were no differences in ˙ O2peak between baseline (as recorded in the second CPET) V and 6 months in the usual care group. It could be speculated that had we not conducted two CPET at baseline, the in˙ O2peak may have been inflated to 12% (27.0 vs crease in V 30.1 mLIkgj1Iminj1) in the exercise group and increased in the usual care group (27.9 vs 29.2 mLIkgj1Iminj1). Interestingly, in a meta-analysis of six randomized controlled trials assessing the efficacy of exercise training on direct ˙ O2peak in patients with cancer, the mean measurement of V ˙ increase in VO2peak was 2.91 mLIkgj1Iminj1 or approximately 12% compared with that in controls (19). It is important to note that all of these trials conducted only one CPET at baseline. On the basis of the present findings, testing variability may have contributed to the observed improvements. Although some testing variability could potentially be controlled for by comparing changes in exercise groups with those in controls groups, our findings raise important questions regarding CPET methodology before, during, or after intervention and for cardiovascular risk assessment in the oncology setting. For example, given that ˙ O2peak decreased in 28% of subjects on test 2 in the the V present investigation, future studies should examine whether the highest data point, the mean of two points, or the second data point should be used for final baseline assessments. To accurately assess test–retest reliability, it is important to adhere to stringent CPET methodology. To this end, we
˙ E/V ˙ CO2) FIGURE 2—Bland–Altman plot for submaximal variables: (V (A) and VT (B).
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have been inherent variability in the effort that deconditioned subjects were willing to exert from day to day (21). To this end, there were variations in HR between tests, suggesting inconsistency of effort. Third, there is also considerable ˙ O2peak occurs, depending on how technical variation when V many breaths occur during the sampling period (30 s for the present investigation). A small change may be associated with when the gas sampling occurs in comparison to breathing pattern. Finally, this was a prespecified substudy of a randomized trial with a modest sample size. In summary, the findings of the present study demonstrating an increase in maximal and submaximal CPETderived measures in the second test among men with clinically localized PC suggest that two baseline CPET are required, when feasible, in all studies examining the efficacy ˙ O2peak in the oncology setting. Imporof interventions on V tantly, analyses of similar studies in both children and adult patients with cancer that include evaluation of CPET before, during, and after therapy are now required to establish standardized methodology and interpretation of results, to formulate reference values, and to increase the clinical utility of CPET. Such efforts will lead to the development of standardized CPET guidelines/recommendations for patients with cancer. This study was supported by a research grant from the National Cancer Institute (R21-CA133895) awarded to L. W. J. The authors declare no conflicts of interest. The results of the present study do not constitute endorsement by the American College of Sports Medicine.
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8. Elborn JS, Stanford CF, Nicholls DP. Reproducibility of cardiopulmonary parameters during exercise in patients with chronic cardiac failure. The need for a preliminary test. Eur Heart J. 1990; 11(1):75–81. 9. Ficarra V, Novara G, Galfano A, et al. Twelve-month self-reported quality of life after retropubic radical prostatectomy: a prospective study with Rand 36-Item Health Survey (Short Form-36). BJU Int. 2006;97(2):274–8. 10. Fletcher GF, Ades PA, Kligfield P, et al. Exercise standards for testing and training: a scientific statement from the American Heart Association. Circulation. 2013;128(8):873–934. 11. Hawkins MN, Raven PB, Snell PG, Stray-Gundersen J, Levine BD. Maximal oxygen uptake as a parametric measure of cardiorespiratory capacity. Med Sci Sports Exerc. 2007;39(1):103–7. 12. Hunt SA, Abraham WT, Chin MH, et al. 2009 focused update incorporated into the ACC/AHA 2005 guidelines for the diagnosis and management of heart failure in adults a report of the American College of Cardiology Foundation/American Heart Association Task Force on practice guidelines developed in collaboration with the International Society for Heart and Lung Transplantation. J Am Coll Cardiol. 2009;53(15):e1–90. 13. Janicki JS, Gupta S, Ferris ST, McElroy PA. Long-term reproducibility of respiratory gas exchange measurements during exercise in patients with stable cardiac failure. Chest. 1990; 97(1):12–7.
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adhered to the following procedures: standardized participant instructions, testing at the same time of the day, screening for intercurrent acute illness or injury or change in condition, calibration and validation of the gas exchange unit before each test, and strong encouragement to reach volitional exhaustion or symptom limitation. However, there were several factors and testing methodology limitations that may contribute to increased variability in the measurement of peak and submaximal CPET parameters. First, to facilitate the achievement of peak aerobic capacity in a timely and standardized way, several maximum incremental ramp protocols are available. These protocols are classified according to the application of work rate, as follows: constant increments (i.e., application of the same workload increments for all patients) or individualized increments (i.e., variable workload increments based on patient characteristics). We used individualized protocols, as recommended by the American Thoracic Society (2). Individualized protocols enable the selection of workload increments that are appropriate for a patient. Such flexibility is particularly useful for CPET of patients with cancer, many of whom have been treated with cytotoxic combination therapy and present with concomitant comorbid disease (16). Second, there is considerable day-to-day biological variation in humans that is well documented in healthy subjects (11). In patients with a chronic condition on a variety of medications, the biological variance could be even greater. Indeed, although all subjects in the present investigation achieved the maximal effort as outlined by the American Thoracic Society (2), there may
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14. Jones LW, Courneya KS, Mackey JR, et al. Cardiopulmonary function and age-related decline across the breast cancer survivorship continuum. J Clin Oncol. 2012;30(20):2530–7. 15. Jones LW, Douglas PS, Eves ND, et al. Rationale and design of the Exercise Intensity Trial (EXCITE): a randomized trial comparing the effects of moderate versus moderate to high-intensity aerobic training in women with operable breast cancer. BMC Cancer. 2010;10:531. 16. Jones LW, Eves ND, Haykowsky M, Joy AA, Douglas PS. Cardiorespiratory exercise testing in clinical oncology research: systematic review and practice recommendations. Lancet Oncol. 2008;9(8):757–65. 17. Jones LW, Eves ND, Mackey JR, et al. Safety and feasibility of cardiopulmonary exercise testing in patients with advanced cancer. Lung Cancer. 2007;55(2):225–32. 18. Jones LW, Hornsby W, Freedland SJ, et al. Effects of nonlinear aerobic training on erectile dysfunction and cardiovascular function following radical prostatectomy for clinically localized prostate cancer. Eur Urol. 2014;65(5):852–5. 19. Jones LW, Liang Y, Pituskin EN, et al. Effect of exercise training on peak oxygen consumption in patients with cancer: a metaanalysis. Oncologist. 2011;16(1):112–20. 20. Jones LW, Watson D, Herndon JE 2nd, et al. Peak oxygen consumption and long-term all-cause mortality in nonsmall cell lung cancer. Cancer. 2010;116(20):4825–32.
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21. Katzel LI, Sorkin JD, Macko RF, Smith B, Ivey FM, Shulman LM. Repeatability of aerobic capacity measurements in Parkinson disease. Med Sci Sports Exerc. 2011;43(12):2381–7. 22. Mina DS, Matthew AG, Trachtenberg J, et al. Physical activity and quality of life after radical prostatectomy. Can Urol Assoc J. 2010;4(3):180–6. 23. Ottenbacher AJ, Day RS, Taylor WC, et al. Long-term physical activity outcomes of home-based lifestyle interventions among breast and prostate cancer survivors. Support Care Cancer. 2012;20(10):2483–9. 24. Quinn M, Babb P. Patterns and trends in prostate cancer incidence, survival, prevalence and mortality. Part I: international comparisons. BJU Int. 2002;90(2):162–73. 25. Scott JM, Haykowsky MJ, Eggebeen J, Morgan TM, Brubaker PH, Kitzman DW. Reliability of peak exercise testing in patients with heart failure with preserved ejection fraction. Am J Cardiol. 2012;110(12):1809–13. 26. Wasserman K, McIlroy MB. Detecting the threshold of anaerobic metabolism in cardiac patients during exercise. Am J Cardiol. 1964;14:844–52. 27. Win T, Jackson A, Groves AM, Sharples LD, Charman SC, Laroche CM. Comparison of shuttle walk with measured peak oxygen consumption in patients with operable lung cancer. Thorax. 2006;61(1):57–60.
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ABSTRACT SCOTT, J. M., W. E. HORNSBY, A. LANE, A. A. KENJALE, N. D. EVES, and L. W. JONES. Reliability of Maximal Cardiopulmonary Exercise Testing in Men with Prostate Cancer. Med. Sci. Sports Exerc., Vol. 47, No. 1, pp. 27–32, 2015. Purpose: To accurately assess exercise interventions and to evaluate acute and chronic cardiovascular effects in patients with early-stage cancer, consistently reliable functional outcome measures must be obtained. An incremental cardiopulmonary exercise test (CPET) with gas exchange ˙ O2peak) provides the gold standard outcome of cardiorespiratory fitness. Methods: In measurement to assess peak oxygen consumption (V the context of a randomized controlled trial, 40 patients with prostate cancer (mean age, 59 T 7 yr) after radical prostatectomy performed two maximal CPET within 5.6 T 5.5 d of each other. Incremental treadmill tests were performed in the morning under identical laboratory conditions. Reliability and within-subject variability from test 1 to test 2 for peak and submaximal variables were assessed by correlation coefficients, intraclass correlations (ICC), Bland–Altman plots, coefficient of variation, and paired t-tests. Results: There was high ˙ O2peak (r = 0.92; P G 0.001; ICC, 0.900), ventilatory threshold (r = 0.88; P G 0.001; ICC, 0.927), minute reliability between CPET for V ˙ E/V ˙ CO2) (r = 0.86; P G 0.001; ICC, 0.850), and peak heart rate (r = 0.95; P G 0.001; ventilation–carbon dioxide production relation (V ICC, 0.944). However, high within-subject variability was observed for all CPET parameters (mean coefficient of variation, 4.7%). ˙ O2peak (27.0 T 5.6 vs 28.1 T 5.3 mLIkgj1Iminj1, Compared with those for test 1, significantly higher mean values were observed for V ˙ E/V ˙ CO2 (31.3 T 5.8 vs 32.8 T 3.4, P G 0.05) in test 2. P G 0.05), ventilatory threshold (1.91 T 0.5 vs 1.97 T 0.4 LIminj1, P G 0.05), and V Conclusions: These findings indicate the presence of significant, and potentially clinically important, variability in CPET procedures in men with clinically localized prostate cancer and have important implications for the application and use of CPET to evaluate the efficacy of interventions to improve aerobic capacity in the oncology setting. Key Words: TEST REPRODUCIBILITY, PROSTATE CANCER, ONCOLOGY, CARDIOVASCULAR FITNESS
P
have proposed that aerobic-based exercise training may improve cardiorespiratory fitness and cardiovascular risk profiles in patients with PC (18,23). However, to accurately assess exercise interventions and evaluate acute and chronic cardiovascular late effects in patients with an early-stage disease, consistently reliable functional outcome measures must be obtained. Over the past half decade, noninvasive cardiopulmonary exercise testing (CPET) has emerged as a research and clinical tool of immense value given its ability to accurately ˙ O2peak) (which, in turn, can be evaluate aerobic capacity (V used for risk stratification or evaluation of intervention efficacy), to assess the principal determinants of exercise intolerance, and to develop individualized aerobic training prescriptions (14,16,17). Importantly, the within-patient variability of CPET variables in PC has not been ascertained. Consequently, establishing repeatability of CPET in PC is critical not only to ensure accurate assessment of changes in cardiorespiratory fitness across interventions but also to precisely characterize acute and chronic cardiovascular effects for risk stratification. Accordingly, as a prespecified substudy of a randomized trial investigating the efficacy of aerobic training in men with clinically localized ˙ O2peak PC after RP, we evaluated the reproducibility of V
rostate cancer (PC) is the most common non-skin cancer diagnosis among North American men (1). Radical prostatectomy (RP), a primary treatment for early-stage localized PC, is associated with 10-yr survival rates of approximately 90% (1,24). However, RP’s side effects include urinary incontinence, erectile dysfunction, pain, and reduced physical functioning (6). Collectively, these side effects negatively affect health-related quality of life for up to 12 months after surgery (9). Despite significant advances in pharmacotherapy, continuing development of new interventions to improve health-related quality of life remains a high priority for this patient population (22). We, and others,
Address for correspondence: Lee W. Jones, Ph.D., Cardiology Service, Department of Medicine, Memorial Sloan Kettering Cancer Center, New York, NY 10065; E-mail: [email protected]. Submitted for publication March 2014. Accepted for publication April 2014. 0195-9131/15/4701-0027/0 MEDICINE & SCIENCE IN SPORTS & EXERCISEÒ Copyright Ó 2014 by the American College of Sports Medicine DOI: 10.1249/MSS.0000000000000370
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Reliability of Maximal Cardiopulmonary Exercise Testing in Men with Prostate Cancer
CLINICAL SCIENCES
and other important CPET parameters to assess the need for repeat testing.
METHODS Patient cohort, setting, and procedures. This is a secondary analysis of baseline data obtained in the context of a randomized trial investigating the efficacy of aerobic training in men with clinically localized PC after RP. The full details of the study methods have been reported previously (18). In brief, the major eligibility criteria were as follows: 1) e4 months from RP to study enrollment, 2) no absolute contraindications to a maximal CPET, 3) willingness to travel to Duke University Medical Center, 4) primary attending urologist’s ˙ O2peak (mLIkgj1Iminj1) below that of ageapproval, and 5) V matched sedentary normative values (18). All study procedures were reviewed and approved by the Duke University Medical Center institutional review boards. All subjects signed a written consent before the initiation of any study-related procedures. After the initial eligibility determination, all patients performed a maximal CPET as part of the study’s screening procedures (visit 1). If no CPET-related adverse events were detected, all patients returned to perform a repeat CPET (visit 2). Maximal CPET procedures. All CPET were performed using an incremental treadmill test (modified Balke protocol) on a motorized treadmill with 12-lead ECG monitoring (MacÒ 5000; GE Healthcare). Participants were provided with detailed, standardized, verbal instructions before each test and were told to avoid exercise, caffeine, and alcohol for 24 h and consume medications as usual. All testing was performed between 8:00 and 10:00 a.m. Complete calibration of gas concentrations using primary standard gases and flow using a 3-L syringe were performed before each test. All tests were performed by the same two certified exercise physiologists. To avoid bias, testers intentionally did not view the results of test 1 immediately before conducting test 2. Before beginning the test, subjects were familiarized with the mouthpiece and walking on the treadmill for approximately 10 min, followed by 10 min of rest. After stable resting metabolic values were achieved (including blood pressure and HR), subjects began walking at a pace selected in the warm-up as a comfortable but brisk pace (approximately 2.5–4.0 mph) at 0% grade for 2 min. During the test, participants were encouraged to walk for as long as possible, resulting in a peak, symptom-limited, exhaustive effort. Grade was increased every 2 min until ventilatory threshold (VT) (determined independently in each test) and then every minute thereafter until exhaustion or a symptom limitation (15). RPE were evaluated at the end of each workload using the modified Borg scale. Whether patients gave a maximal effort was determined on the basis of a combination of symptoms (dyspnea on exertion and/or fatigue as primary end points) and physiological measures (defined as a plateau in oxygen consumption during the final stage, HRmax 9 85% of age-adjusted predicted HRmax, and RER 9 1.10) (10). Metabolic gas exchange was measured continuously during exercise and averaged over 30-s intervals (Parvo Medics ˙ O2peak was TrueOneÒ 2400; Parvo Medics, Sandy, UT). V
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˙ O2 value for a given 30-s interval within defined as the highest V ˙ O2 at VT was independently the last 60 s of exercise. The V determined by a blinded reader using standard methods (2,26). ˙ E/ The minute ventilation–carbon dioxide production relation (V ˙ CO2 slope) was determined by measuring the slope across the V entire duration of the test (3). Statistical analyses. Means are expressed using either TSD or 10th and 90th percentiles. Within-subject variability from test 1 to test 2 was evaluated by within-subject absolute change (i.e., either an increase or decrease from test 1 to test 2) and tested using paired samples t-tests. Bland–Altman plots were constructed, defined as the difference in values from test 2 and test 1 plotted versus the average of the values from tests 1 and 2 with SD of the difference (average difference T 1.96 SD of the difference) (7). Reliability of the CPET outcome measures was assessed by Pearson correlations and intraclass correlations (ICC). One-sided 95% confidence intervals (CI) of Pearson correlations were made using the Fisher z transformation. For each variable, the coefficient of variation (CV) was defined as follows: (withinsubject SD/within-subject mean) 100%. Significance for all tests was set at P G 0.05.
RESULTS Participant characteristics. Details regarding response rates and profiles of the participants have been reported previously (18). In brief, 50 patients were randomized in the parent trial and 40 (80%) successfully completed two baseline CPET (2) (Table 1). Participant recruitment TABLE 1. Participant characteristics (n = 40). Variable
Overall (n = 40)
Age (yr) Weight (kg) Body mass index (kgImj2) Race, n (%) White Black Asian Current smoker, n (%) Comorbid conditions, n (%) Hypertension Hyperlipidemia Diabetes mellitus CAD Pulmonary disease None of these comorbid conditions Tumor characteristics PSA PSA category, n (%) G4 4–10.0 10.1–19.9 20.0–49.9 Gleason sum, n (%) G7 Q7 Type of surgery, n (%) Robotic Radical Days from postsurgery to randomization
60 (7) 87.6 (12.8) 28.0 (3.3) 27 11 2 1
(68) (28) (5) (3)
24 22 6 3 12 7
(60) (55) (15) (8) (30) (18)
6.2 (4.2) 7 30 2 1
(18) (75) (5) (3)
18 (45) 22 (55) 15 (38) 25 (63) 74 (38)
Values are expressed as n (%). PSA, Prostate-specific antigen.
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TABLE 2. Reliability of CPET. Test 1 11.3 27.0 2.39 161 31.3 1.91 1.18
T T T T T T T
2.2 5.6 0.5 17 5.8 0.4 0.08
Test 2
R
One-sided 95% CI
ICC
P Value
T T T T T T T
0.750 0.919 0.943 0.949 0.864 0.957 0.670
0.541 0.861 0.856 0.945 0.851 0.790 0.440
0.927 0.900 0.927 0.938 0.864 0.873 0.927
G0.001 G0.001 G0.001 G0.001 G0.001 G0.001 G0.001
11.5 28.1 2.49 163 32.8 1.97 1.19
2.2 5.3 0.5 16 3.4 0.4 0.07
P value corresponds to the R value.
took place between November 2009 and July 2012. The two baseline CPET were separated by 5.6 T 5.5 d. No serious or lifethreatening adverse events were observed during any CPET procedures. During baseline CPET, ischemic ECG changes (Q2.0-mm ST depression) were observed in three patients. Test–retest reliability. Pearson correlations and ICC for peak and submaximal variables are summarized in Table 2. There was a significant correlation between the two tests, with ˙ O2peak, HR), 0.96 correlation coefficients of 0.94 (absolute V (VT), and 0.67 (RER). ICC ranged from 0.927 (absolute ˙ O2peak, RER, exercise time), 0.790 (VT), and 0.938 (HR). V Within-subject test–retest variability. Test–retest variability (CV) for peak and submaximal parameters ranged from ˙ O2peak), and up to 2.2% (HR), 4.2% (indexed and absolute V 7.6% (exercise duration). Exercise duration (11.3 T 2.2 vs 11.5 T ˙ O2peak (2.39 T 0.5 vs 2.49 T 0.5 LIminj1; 27.0 T 5.6 2.2 min), V vs 28.1 T 5.3 mLIkgj1Iminj1; P G 0.01), peak HR (161 T 17 vs 163 T 16 bpm), VT (1.91 T 0.4 vs 1.97 T 0.4 LIminj1), and ˙ E/V ˙ CO2 (32.1 T 5.8 vs 32.8 T 3.4) increased from test 1 to V test 2 (Table 3). The percentage of subjects who increased on test 2 was greater than the percentage of those who decreased ˙ O2peak (72%), exercise time (75%), HR (68%), V ˙ E/ for V ˙ CO2 (83%), and VT (65%). As shown in Figure 1A and B, V there was a high variability between tests for peak variables (95% CI of 25.2–29.8 mLIkgj1Iminj1, 2.2–2.7 LIminj1 ˙ O2peak), and 155–167 bpm (HR)) and submaximal vari(V ˙ E/V ˙ CO2), ables (Fig. 2A and B) (95% CI of 31.0–33.8 (V 1.72–2.09 LIminj1 (VT)). Variability was similar for subjects ˙ O2peak (Figs. 1 and 2). with lower versus those with higher V
DISCUSSION The principal finding of this ancillary analysis was that despite the good test–retest CPET reliability, there was a significant within-subject variability in peak and submaximal variables (CV ranging from 2% to 8%) in men with
localized PC. Accordingly, we contend that our data suggest the need to perform two CPET at baseline to obtain valid ˙ O2peak and other CPET results in men after RP for baseline V clinically localized PC. Such variability has critical impli˙ O2 data, cations for the acquisition of accurate baseline V which, in turn, could affect prognosis and risk stratification ˙ O2 in and the magnitude of intervention efficacy to change V patients with cancer. Some studies have closely examined the variability of measurements obtained during CPET in other clinical populations with conflicting results. In the ‘‘Heart Failure: A Controlled Trial Investigating Outcomes of Exercise TraiNing ˙ O2peak was not different in (HF-ACTION)’’ trial, the mean V test 1 and 2 (15.2 T 5.0 vs 15.2 T 5.0 mLIkgj1Iminj1, P = 0.78) (5). However, there was a large within-subject variability ˙ O2peak, which the authors attributed to variations (6.6%) for V in subject factors specific to patients with heart failure such as daily hemodynamic and volume status fluctuations. A more recent investigation involving patients with heart failure with ˙ O2peak preserved ejection fraction reported no difference in V between tests 1 and 2 (14.4 vs 14.3 mLIkgj1Iminj1), with authors concluding that the incremental gain in information should be balanced by the increase in participant burden and cost (25). In contrast, current CPET guidelines in clinical populations with cardiovascular and respiratory disease recommend that at least two CPET be conducted in all clinical and research settings; these recommendations were formulated on the basis of previous work demonstrating that ˙ O2peak significantly varies over serial tests (2,12). For examV ple, Elborn et al. (8) performed three consecutive treadmillbased CPET separated by 2 wk in 30 subjects with heart ˙ O2peak improved significantly from failure. The mean V the first to the second test (14.1 vs 14.9 mLIkgj1Iminj1, P G 0.005), with no difference between tests 2 and 3 whereas the average within-subject CV was 6%. These find˙ O2peak ings are consistent with those observed here, in which V increased significantly from 27.0 to 28.1 mLIkgj1Iminj1 and
TABLE 3. Test–retest variability of CPET variables. Test 1 Exercise time (min) Indexed oxygen uptake (mLIkgj1Iminj1) Absolute oxygen uptake (LIminj1) HR (bpm) VT (LIminj1) Ventilation per carbon dioxide slope RER
11.3 27.0 2.39 161 1.91 32.1 1.18
(9.0, 15.0) (20.9, 33.7) (1.86, 2.97) (146, 187) (1.37, 2.29) (29.1, 37.1) (1.11, 1.31)
Test 2 11.5 28.1 2.49 163 1.97 32.8 1.19
(9, 14.5) (22.3, 34.9) (1.92, 3.03) (146, 184) (1.43, 2.45) (29.0, 37.3) (1.11, 1.32)
P Value
Absolute Change (2 – 1)
%291
%192
CV (%)
0.35 0.003 0.001 0.14 0.01 0.02 0.14
0.23 1.1 0.10 2 0.07 0.65 0.01
75 72 72 68 65 83 65
25 28 28 32 35 17 35
7.6 4.2 4.2 2.2 7.5 2.9 3.1
Values are expressed as mean (10th percentile, 90th percentile) unless noted otherwise. P value corresponds to a paired t-test of the null hypothesis that the mean of test 2 j the mean of test 1 = 0.
CPET RELIABILITY IN PROSTATE CANCER
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Exercise time (min) Indexed peak oxygen uptake (mLIkgj1Iminj1) Absolute peak oxygen uptake (LIminj1) HR (bpm) Ventilation per carbon dioxide slope Oxygen uptake at VT (LIminj1) RER
CLINICAL SCIENCES ˙ O2peak (A) and FIGURE 1—Bland–Altman plot for peak variables: V peak HR (B).
the within-subject CV was 4.2%. In addition, the percentage of subjects who increased on test 2 (72%) was greater than the percentage of those who decreased (28%). Submaximal re˙ E/V ˙ CO2 slope have been used with sponses such as VT and V greater frequency to classify exercise intolerance and to riskstratify in clinical populations (5,25). In contrast to previous investigations on patients with heart failure reporting nearly identical mean values on tests 1 and 2 for submaximal indices (5,25), here, we found that 83% (33/40) and 65% ˙ E/V ˙ CO2 slope and VT, re(26/40) of subjects increased V spectively, on test 2. Taken together, these findings are indicative of variability in men with localized PC. We did not conduct a third CPET; however, on the basis of previous literature, an additional test is unlikely to provide clinically relevant changes (8,13,21). The variability in both maximal and submaximal CPET parameters observed in the present study is potentially clinically meaningful. For example, there is growing evi˙ O2 for both prognostic (14,20) dence supporting the use of V and risk stratification (4,27) purposes in numerous oncology clinical scenarios. These findings underscore the significance of accurate CPET-derived peak and submaximal measures, particularly given the increasing number of cancer diagnoses combined with the large and rapidly growing number of cancer survivors who could benefit from a global measure of the integrative capacity of the pulmonary, cardiovascular, and skeletal muscle systems to deliver and use O2. Furthermore, in the parent trial, we found that mean
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˙ O2peak increased from 28.1 mLIkgj1Iminj1 at baseline (as V recorded in the second CPET) to 30.1 mLIkgj1Iminj1 at week 24, an increase of 9% among patients randomized to supervised aerobic training. There were no differences in ˙ O2peak between baseline (as recorded in the second CPET) V and 6 months in the usual care group. It could be speculated that had we not conducted two CPET at baseline, the in˙ O2peak may have been inflated to 12% (27.0 vs crease in V 30.1 mLIkgj1Iminj1) in the exercise group and increased in the usual care group (27.9 vs 29.2 mLIkgj1Iminj1). Interestingly, in a meta-analysis of six randomized controlled trials assessing the efficacy of exercise training on direct ˙ O2peak in patients with cancer, the mean measurement of V ˙ increase in VO2peak was 2.91 mLIkgj1Iminj1 or approximately 12% compared with that in controls (19). It is important to note that all of these trials conducted only one CPET at baseline. On the basis of the present findings, testing variability may have contributed to the observed improvements. Although some testing variability could potentially be controlled for by comparing changes in exercise groups with those in controls groups, our findings raise important questions regarding CPET methodology before, during, or after intervention and for cardiovascular risk assessment in the oncology setting. For example, given that ˙ O2peak decreased in 28% of subjects on test 2 in the the V present investigation, future studies should examine whether the highest data point, the mean of two points, or the second data point should be used for final baseline assessments. To accurately assess test–retest reliability, it is important to adhere to stringent CPET methodology. To this end, we
˙ E/V ˙ CO2) FIGURE 2—Bland–Altman plot for submaximal variables: (V (A) and VT (B).
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have been inherent variability in the effort that deconditioned subjects were willing to exert from day to day (21). To this end, there were variations in HR between tests, suggesting inconsistency of effort. Third, there is also considerable ˙ O2peak occurs, depending on how technical variation when V many breaths occur during the sampling period (30 s for the present investigation). A small change may be associated with when the gas sampling occurs in comparison to breathing pattern. Finally, this was a prespecified substudy of a randomized trial with a modest sample size. In summary, the findings of the present study demonstrating an increase in maximal and submaximal CPETderived measures in the second test among men with clinically localized PC suggest that two baseline CPET are required, when feasible, in all studies examining the efficacy ˙ O2peak in the oncology setting. Imporof interventions on V tantly, analyses of similar studies in both children and adult patients with cancer that include evaluation of CPET before, during, and after therapy are now required to establish standardized methodology and interpretation of results, to formulate reference values, and to increase the clinical utility of CPET. Such efforts will lead to the development of standardized CPET guidelines/recommendations for patients with cancer. This study was supported by a research grant from the National Cancer Institute (R21-CA133895) awarded to L. W. J. The authors declare no conflicts of interest. The results of the present study do not constitute endorsement by the American College of Sports Medicine.
REFERENCES 1. American Cancer Society [Internet]. Atlanta: American Cancer Society. Available from: http://www.cancer.org/research/cancerfactsstatistics/ cancerfactsfigures2013/index. Accessed February 21, 2014. 2. American Thoracic Society; American College of Chest Physicians. ATS/ACCP statement on cardiopulmonary exercise testing. Am J Respir Crit Care Med. 2003;167(2):211–77. 3. Arena R, Myers J, Aslam SS, Varughese EB, Peberdy MA. Technical considerations related to the minute ventilation/carbon dioxide output slope in patients with heart failure. Chest. 2003; 124(2):720–7. 4. Beckles MA, Spiro SG, Colice GL, Rudd RM. Initial evaluation of the patient with lung cancer: symptoms, signs, laboratory tests, and paraneoplastic syndromes. Chest. 2003;123(1 Suppl):97S–104S. 5. Bensimhon DR, Leifer ES, Ellis SJ, et al. Reproducibility of peak oxygen uptake and other cardiopulmonary exercise testing parameters in patients with heart failure (from the Heart Failure and A Controlled Trial Investigating Outcomes of exercise traiNing). Am J Cardiol. 2008;102(6):712–7. 6. Bhatnagar V, Stewart ST, Huynh V, Jorgensen G, Kaplan RM. Estimating the risk of long-term erectile, urinary and bowel symptoms resulting from prostate cancer treatment. Prostate Cancer Prostatic Dis. 2006;9(2):136–46. 7. Bland JM, Altman DG. Statistical methods for assessing agreement between two methods of clinical measurement. Lancet. 1986;1(8476):307–10.
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8. Elborn JS, Stanford CF, Nicholls DP. Reproducibility of cardiopulmonary parameters during exercise in patients with chronic cardiac failure. The need for a preliminary test. Eur Heart J. 1990; 11(1):75–81. 9. Ficarra V, Novara G, Galfano A, et al. Twelve-month self-reported quality of life after retropubic radical prostatectomy: a prospective study with Rand 36-Item Health Survey (Short Form-36). BJU Int. 2006;97(2):274–8. 10. Fletcher GF, Ades PA, Kligfield P, et al. Exercise standards for testing and training: a scientific statement from the American Heart Association. Circulation. 2013;128(8):873–934. 11. Hawkins MN, Raven PB, Snell PG, Stray-Gundersen J, Levine BD. Maximal oxygen uptake as a parametric measure of cardiorespiratory capacity. Med Sci Sports Exerc. 2007;39(1):103–7. 12. Hunt SA, Abraham WT, Chin MH, et al. 2009 focused update incorporated into the ACC/AHA 2005 guidelines for the diagnosis and management of heart failure in adults a report of the American College of Cardiology Foundation/American Heart Association Task Force on practice guidelines developed in collaboration with the International Society for Heart and Lung Transplantation. J Am Coll Cardiol. 2009;53(15):e1–90. 13. Janicki JS, Gupta S, Ferris ST, McElroy PA. Long-term reproducibility of respiratory gas exchange measurements during exercise in patients with stable cardiac failure. Chest. 1990; 97(1):12–7.
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adhered to the following procedures: standardized participant instructions, testing at the same time of the day, screening for intercurrent acute illness or injury or change in condition, calibration and validation of the gas exchange unit before each test, and strong encouragement to reach volitional exhaustion or symptom limitation. However, there were several factors and testing methodology limitations that may contribute to increased variability in the measurement of peak and submaximal CPET parameters. First, to facilitate the achievement of peak aerobic capacity in a timely and standardized way, several maximum incremental ramp protocols are available. These protocols are classified according to the application of work rate, as follows: constant increments (i.e., application of the same workload increments for all patients) or individualized increments (i.e., variable workload increments based on patient characteristics). We used individualized protocols, as recommended by the American Thoracic Society (2). Individualized protocols enable the selection of workload increments that are appropriate for a patient. Such flexibility is particularly useful for CPET of patients with cancer, many of whom have been treated with cytotoxic combination therapy and present with concomitant comorbid disease (16). Second, there is considerable day-to-day biological variation in humans that is well documented in healthy subjects (11). In patients with a chronic condition on a variety of medications, the biological variance could be even greater. Indeed, although all subjects in the present investigation achieved the maximal effort as outlined by the American Thoracic Society (2), there may
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14. Jones LW, Courneya KS, Mackey JR, et al. Cardiopulmonary function and age-related decline across the breast cancer survivorship continuum. J Clin Oncol. 2012;30(20):2530–7. 15. Jones LW, Douglas PS, Eves ND, et al. Rationale and design of the Exercise Intensity Trial (EXCITE): a randomized trial comparing the effects of moderate versus moderate to high-intensity aerobic training in women with operable breast cancer. BMC Cancer. 2010;10:531. 16. Jones LW, Eves ND, Haykowsky M, Joy AA, Douglas PS. Cardiorespiratory exercise testing in clinical oncology research: systematic review and practice recommendations. Lancet Oncol. 2008;9(8):757–65. 17. Jones LW, Eves ND, Mackey JR, et al. Safety and feasibility of cardiopulmonary exercise testing in patients with advanced cancer. Lung Cancer. 2007;55(2):225–32. 18. Jones LW, Hornsby W, Freedland SJ, et al. Effects of nonlinear aerobic training on erectile dysfunction and cardiovascular function following radical prostatectomy for clinically localized prostate cancer. Eur Urol. 2014;65(5):852–5. 19. Jones LW, Liang Y, Pituskin EN, et al. Effect of exercise training on peak oxygen consumption in patients with cancer: a metaanalysis. Oncologist. 2011;16(1):112–20. 20. Jones LW, Watson D, Herndon JE 2nd, et al. Peak oxygen consumption and long-term all-cause mortality in nonsmall cell lung cancer. Cancer. 2010;116(20):4825–32.
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21. Katzel LI, Sorkin JD, Macko RF, Smith B, Ivey FM, Shulman LM. Repeatability of aerobic capacity measurements in Parkinson disease. Med Sci Sports Exerc. 2011;43(12):2381–7. 22. Mina DS, Matthew AG, Trachtenberg J, et al. Physical activity and quality of life after radical prostatectomy. Can Urol Assoc J. 2010;4(3):180–6. 23. Ottenbacher AJ, Day RS, Taylor WC, et al. Long-term physical activity outcomes of home-based lifestyle interventions among breast and prostate cancer survivors. Support Care Cancer. 2012;20(10):2483–9. 24. Quinn M, Babb P. Patterns and trends in prostate cancer incidence, survival, prevalence and mortality. Part I: international comparisons. BJU Int. 2002;90(2):162–73. 25. Scott JM, Haykowsky MJ, Eggebeen J, Morgan TM, Brubaker PH, Kitzman DW. Reliability of peak exercise testing in patients with heart failure with preserved ejection fraction. Am J Cardiol. 2012;110(12):1809–13. 26. Wasserman K, McIlroy MB. Detecting the threshold of anaerobic metabolism in cardiac patients during exercise. Am J Cardiol. 1964;14:844–52. 27. Win T, Jackson A, Groves AM, Sharples LD, Charman SC, Laroche CM. Comparison of shuttle walk with measured peak oxygen consumption in patients with operable lung cancer. Thorax. 2006;61(1):57–60.
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