ORIGINAL CONTRIBUTION
Impact of BMI on Postoperative Outcomes in Patients Undergoing Proctectomy for Rectal Cancer: A National Surgical Quality Improvement Program Analysis Radhika K. Smith, M.D.1 • Robyn B. Broach, Ph.D.2 • Traci L. Hedrick, M.D.3 Najjia N. Mahmoud, M.D.4 • E. Carter Paulson, M.D., M.S.C.E.4 1 Department of General Surgery, Temple University Hospital, Philadelphia, Pennsylvania 2 Department of Surgery, Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania 3 Division of Colon and Rectal Surgery, University of Virginia Health System, Charlottesville, Virginia 4 Division of Colon and Rectal Surgery, Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania
BACKGROUND: There is a mounting body of evidence that suggests worsened postoperative outcomes at the extremes of BMI, yet few studies investigate this relationship in patients undergoing proctectomy for rectal cancer. OBJECTIVE: We aimed to examine the relationship between BMI and short-term outcomes after proctectomy for cancer. DESIGN: This was a retrospective study comparing the outcomes of patients undergoing proctectomy for rectal cancer as they relate to BMI. SETTINGS: The American College of Surgeons-National Surgical Quality Improvement Program database was queried for this study. PATIENTS: Patients included were those who underwent proctectomy for rectal neoplasm between 2005 and 2011. MAIN OUTCOME MEASURES: Study end points included 30-day mortality and overall morbidity, including the receipt of blood transfusion, venous thromboembolic disease, wound dehiscence, renal failure, reintubation, cardiac complications, readmission, reoperation, and infectious complications (surgical site infection, intraabdominal abscess, pneumonia, and urinary tract Financial Disclosure: None reported. Correspondence: E. Carter Paulson, M.D., M.S.C.E., 3900 Woodland Ave, 5th Floor, Surgical Business Office, Philadelphia, PA 19104. E-mail: [email protected] Dis Colon Rectum 2014; 57: 687–693 DOI: 10.1097/DCR.0000000000000097 © The ASCRS 2014 Diseases of the Colon & Rectum Volume 57: 6 (2014)
infection). Univariate logistic regression was used to analyze differences among patients of varying BMI ranges (kg/m2; ≤20, 20-24, 25-29, 30-34, and ≥35). When significant differences were found, multivariable logistic regression, adjusting for preoperative demographic and clinical variables, was performed. RESULTS: A total of 11,995 patients were analyzed in this study. The incidences of overall morbidity, wound infection, urinary tract infection, venous thromboembolic event, and sepsis were highest in those patients with a BMI of ≥35 kg/m2 (OR, 1.63, 3.42, 1.47, 1.64, and 1.50). Wound dehiscence was also significantly more common in heavier patients. Patients with a BMI 50 years of age, the prevalence of obesity has increased at an alarming rate. Currently, 35.7% of the US population is obese (BMI ≥30 kg/m2), and 5.7% is severely obese (BMI, ≥40 kg/m2).3 This rate continues to rise, with a projected 33% increase in obesity prevalence and a 130% increase in severe obesity prevalence by 2030. This expected increase is associated with a $549.5 billion increase in healthcare costs.4 It is recognized that obesity is associated with an increase in complications after a variety of both colorectal and noncolorectal procedures.5–7 Institutional series have established an association between increased BMI and longer operative times, higher intraoperative blood loss, prolonged duration of ileus, and increased length of stay.8– 10 Aytac et al11 demonstrated an increased rate of anastomotic leak in the obese population, and many studies have defined a rate of surgical site infections as high as 60% among these patients.12–15 To date, however, there have been no large studies looking at the effects of obesity on the short-term outcomes in proctectomy for rectal cancer using a national sampling. In contrast, it is also well described that underweight patients experience higher postoperative morbidity and mortality when compared with patients with a normal BMI. This U-shaped relationship between BMI and postoperative complications has been demonstrated after many procedures, including coronary artery bypass grafting, inguinal hernia repair, and pancreatic resections,16–21 but has not been examined in the population with rectal cancer. However, this may represent a specific challenge for patients with advanced rectal cancer, many of whom undergo neoadjuvant chemoradiotherapy and are at high risk for preoperative weight loss and cachexia. Examining the effect that low BMI has on short-term outcomes after proctectomy may identify a vulnerable patient population for whom preoperative intervention, such as nutritional supplementation, may help reduce postoperative complications. In this study, we use the American College of Surgeons-National Surgical Quality Improvement Program (ACS-NSQIP) database to examine the relationship between BMI and postoperative morbidity and mortality after rectal cancer surgery. We anticipate that both obesity and a low BMI will be associated with increased rates of postoperative complications.
MATERIALS AND METHODS Study Design
After approval by the University of Pennsylvania Health System Institutional Review Board, an observational multi-institutional cohort study was conducted through
SMITH ET AL: BMI AND OUTCOMES IN RECTAL RESECTION
query of the ACS-NSQIP database. NSQIP methodology has been described previously22,23 and includes national data from a random sampling of general and vascular surgery procedures performed at participating academic and community institutions. More than 100 variables are collected and cataloged into a database by a dedicated clinically trained staff. These variables include demographic data, patient comorbidities, select 30-day preoperative laboratory values, operative type, and 30-day postoperative morbidity and mortality. Study Inclusion
NSQIP data collected between 2005 and 2011 was queried for patients with an International Classification of Diseases, Ninth Revision, code of 154.1 (cancer of the rectum). Those patients undergoing proctectomy were identified by the Current Procedural Terminology codes of 45110 (abdominoperineal resection), 45395 (laparoscopic abdominoperineal resection), 44145 (low anterior resection), 44146 (low anterior resection with colostomy), 44147 (proctectomy partial, abdominal and perineal), 45112 (low anterior resection with coloanal anastomosis), 45119 (proctectomy with coloanal anastomosis and colonic pouch), 44207 (laparoscopic low anterior resection), 45397 (laparoscopic low anterior resection with colonic pouch), 44208 (laparoscopic low anterior resection with colostomy), 45126 (proctectomy with pelvic exenteration), and 45114 (proctectomy with sacrectomy). Patients without height and weight measurements were excluded from analysis. BMI was defined as the individual’s body weight divided by the square of his or her height (kilograms per meter squared). Patients were stratified according to BMI into 5 groups (kg/m2;
Impact of BMI on Postoperative Outcomes in Patients Undergoing Proctectomy for Rectal Cancer: A National Surgical Quality Improvement Program Analysis Radhika K. Smith, M.D.1 • Robyn B. Broach, Ph.D.2 • Traci L. Hedrick, M.D.3 Najjia N. Mahmoud, M.D.4 • E. Carter Paulson, M.D., M.S.C.E.4 1 Department of General Surgery, Temple University Hospital, Philadelphia, Pennsylvania 2 Department of Surgery, Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania 3 Division of Colon and Rectal Surgery, University of Virginia Health System, Charlottesville, Virginia 4 Division of Colon and Rectal Surgery, Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania
BACKGROUND: There is a mounting body of evidence that suggests worsened postoperative outcomes at the extremes of BMI, yet few studies investigate this relationship in patients undergoing proctectomy for rectal cancer. OBJECTIVE: We aimed to examine the relationship between BMI and short-term outcomes after proctectomy for cancer. DESIGN: This was a retrospective study comparing the outcomes of patients undergoing proctectomy for rectal cancer as they relate to BMI. SETTINGS: The American College of Surgeons-National Surgical Quality Improvement Program database was queried for this study. PATIENTS: Patients included were those who underwent proctectomy for rectal neoplasm between 2005 and 2011. MAIN OUTCOME MEASURES: Study end points included 30-day mortality and overall morbidity, including the receipt of blood transfusion, venous thromboembolic disease, wound dehiscence, renal failure, reintubation, cardiac complications, readmission, reoperation, and infectious complications (surgical site infection, intraabdominal abscess, pneumonia, and urinary tract Financial Disclosure: None reported. Correspondence: E. Carter Paulson, M.D., M.S.C.E., 3900 Woodland Ave, 5th Floor, Surgical Business Office, Philadelphia, PA 19104. E-mail: [email protected] Dis Colon Rectum 2014; 57: 687–693 DOI: 10.1097/DCR.0000000000000097 © The ASCRS 2014 Diseases of the Colon & Rectum Volume 57: 6 (2014)
infection). Univariate logistic regression was used to analyze differences among patients of varying BMI ranges (kg/m2; ≤20, 20-24, 25-29, 30-34, and ≥35). When significant differences were found, multivariable logistic regression, adjusting for preoperative demographic and clinical variables, was performed. RESULTS: A total of 11,995 patients were analyzed in this study. The incidences of overall morbidity, wound infection, urinary tract infection, venous thromboembolic event, and sepsis were highest in those patients with a BMI of ≥35 kg/m2 (OR, 1.63, 3.42, 1.47, 1.64, and 1.50). Wound dehiscence was also significantly more common in heavier patients. Patients with a BMI 50 years of age, the prevalence of obesity has increased at an alarming rate. Currently, 35.7% of the US population is obese (BMI ≥30 kg/m2), and 5.7% is severely obese (BMI, ≥40 kg/m2).3 This rate continues to rise, with a projected 33% increase in obesity prevalence and a 130% increase in severe obesity prevalence by 2030. This expected increase is associated with a $549.5 billion increase in healthcare costs.4 It is recognized that obesity is associated with an increase in complications after a variety of both colorectal and noncolorectal procedures.5–7 Institutional series have established an association between increased BMI and longer operative times, higher intraoperative blood loss, prolonged duration of ileus, and increased length of stay.8– 10 Aytac et al11 demonstrated an increased rate of anastomotic leak in the obese population, and many studies have defined a rate of surgical site infections as high as 60% among these patients.12–15 To date, however, there have been no large studies looking at the effects of obesity on the short-term outcomes in proctectomy for rectal cancer using a national sampling. In contrast, it is also well described that underweight patients experience higher postoperative morbidity and mortality when compared with patients with a normal BMI. This U-shaped relationship between BMI and postoperative complications has been demonstrated after many procedures, including coronary artery bypass grafting, inguinal hernia repair, and pancreatic resections,16–21 but has not been examined in the population with rectal cancer. However, this may represent a specific challenge for patients with advanced rectal cancer, many of whom undergo neoadjuvant chemoradiotherapy and are at high risk for preoperative weight loss and cachexia. Examining the effect that low BMI has on short-term outcomes after proctectomy may identify a vulnerable patient population for whom preoperative intervention, such as nutritional supplementation, may help reduce postoperative complications. In this study, we use the American College of Surgeons-National Surgical Quality Improvement Program (ACS-NSQIP) database to examine the relationship between BMI and postoperative morbidity and mortality after rectal cancer surgery. We anticipate that both obesity and a low BMI will be associated with increased rates of postoperative complications.
MATERIALS AND METHODS Study Design
After approval by the University of Pennsylvania Health System Institutional Review Board, an observational multi-institutional cohort study was conducted through
SMITH ET AL: BMI AND OUTCOMES IN RECTAL RESECTION
query of the ACS-NSQIP database. NSQIP methodology has been described previously22,23 and includes national data from a random sampling of general and vascular surgery procedures performed at participating academic and community institutions. More than 100 variables are collected and cataloged into a database by a dedicated clinically trained staff. These variables include demographic data, patient comorbidities, select 30-day preoperative laboratory values, operative type, and 30-day postoperative morbidity and mortality. Study Inclusion
NSQIP data collected between 2005 and 2011 was queried for patients with an International Classification of Diseases, Ninth Revision, code of 154.1 (cancer of the rectum). Those patients undergoing proctectomy were identified by the Current Procedural Terminology codes of 45110 (abdominoperineal resection), 45395 (laparoscopic abdominoperineal resection), 44145 (low anterior resection), 44146 (low anterior resection with colostomy), 44147 (proctectomy partial, abdominal and perineal), 45112 (low anterior resection with coloanal anastomosis), 45119 (proctectomy with coloanal anastomosis and colonic pouch), 44207 (laparoscopic low anterior resection), 45397 (laparoscopic low anterior resection with colonic pouch), 44208 (laparoscopic low anterior resection with colostomy), 45126 (proctectomy with pelvic exenteration), and 45114 (proctectomy with sacrectomy). Patients without height and weight measurements were excluded from analysis. BMI was defined as the individual’s body weight divided by the square of his or her height (kilograms per meter squared). Patients were stratified according to BMI into 5 groups (kg/m2;
