Clinical Imaging xxx (2015) xxx–xxx
Contents lists available at ScienceDirect
Clinical Imaging journal homepage: http://www.clinicalimaging.org
Magnetic resonance imaging (MRI) evaluation of residual breast tissue following mastectomy and reconstruction with silicone implants Douglas Zippel a,e,⁎, Vered Tsehmaister-Abitbol b, Arie Rundstein b, Anat Shalmon b, Andrew Zbar a, Gil Nardini c, Ilya Novikov d, Miri Sklair-Levy b,e a
Department of Surgery, Chaim Sheba Medical Center, Tel Hashomer, Israel 52621 Department of Diagnostic Imaging, Chaim Sheba Medical Center, Tel Hashomer, Israel 52621 Department of Plastic Surgery, Chaim Sheba, Chaim Sheba Medical Center, Tel Hashomer, Israel 52621 d Gertner Institute for Epidemiology and Health Policy Research, Chaim Sheba Medical Center, Tel Hashomer, Israel 52621 e Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel b c
a r t i c l e
i n f o
Article history: Received 7 September 2014 Received in revised form 16 November 2014 Accepted 9 December 2014 Available online xxxx Keywords: Residual breast tissue Breast cancer Magnetic resonance imaging Breast reconstruction
a b s t r a c t Purpose: We present our use of magnetic resonance (MR) measurement to determine the amount of residual breast tissue (RBT) following total mastectomy with reconstruction. Methods: Breast MR images of 45 women who underwent surgery between January and November 2011 were reviewed. The cohort included therapeutic and prophylactic mastectomies. RBT was evaluated at four points with a digital caliper assessing T2-weighted and T1-weighted images. Results: Patients undergoing mastectomy for carcinoma tended to have less RBT than in prophylactic surgery. Greater age and recent surgery both correlated with larger RBT. Conclusions: Variable thickness of RBT is demonstrable following mastectomy and implant reconstruction using MR imaging. © 2014 Elsevier Inc. All rights reserved.
1. Introduction The use of mastectomy for the primary treatment of breast cancer has increased in recent years [1,2], as has the contralateral prophylactic mastectomy rate in those who have already undergone a prior mastectomy on one side [3]. In particular, with the increased awareness of the role of genetic mutations such as BRCA1 and BRCA2 in breast cancer especially in young women, the use of bilateral mastectomy, with or without immediate reconstruction, has been ever increasing [4]. The clinical issues concerning the use of magnetic resonance imaging (MRI) in such patients have centered on the critical role it plays in the delineation of the diagnosis of multifocal lesions which directly alters the surgical management and influences the mastectomy rate [5,6]. MRI has also been used to assess the reconstructed, mastectomized patient in order to detect locally recurrent disease [7,8]. In this latter setting, breast MRI accurately detects asymptomatic recurrence and defines the extent of disease, although little is currently known concerning its use as a surveillance tool after bilateral mastectomy [9].With the increasing use of bilateral breast MRI, the mastectomized side (reconstructed or not) is in-
⁎ Corresponding author. Department of Surgery, Chaim Sheba Medical Center, Tel Hashomer, Israel 52621. Tel.: +972 3 530 2714; fax: +972 3 534 1562. E-mail address: [email protected] (D. Zippel).
cluded in the field of view (FOV) and should not be dismissed under the assumption that there is no remaining residual breast tissue (RBT). The anatomic breast, although typically described as spanning the second to the sixth ribs, may extend to the clavicle superiorly, to the axilla superolaterally, to the oblique edge of the latissimus dorsi posteriorly, and to the costal margin inferiorly [10]. In addition, the breast may harbor a varying amount of glandular, adipose, and connective tissue, resulting in a wide degree of disparity between individuals. These inherent differences in breast composition, resulting in varying density, may influence the relative risk for carcinoma development [11]. The risk imposed for carcinoma development after a total mastectomy also depends upon the technique used. Skin-sparing mastectomy, which preserves the skin envelope surrounding the breast parenchyma, allows immediate breast reconstruction (IBR) with silicone implants. IBR decreases the requirement for secondary procedure in which surplus skin needs to be recruited using tissue expanders, results in improved body image and high levels of patient satisfaction as well as being oncologically sound [12], and leaves behind minimal RBT [13]. In theory, the amount of RBT will influence the relative risk for residual carcinoma development, although there are only five studies which have previously reported the rates of RBT following mastectomy [13–17]. We present our use of MR measurement to objectively determine the amount of RBT following total mastectomy with breast
http://dx.doi.org/10.1016/j.clinimag.2014.12.014 0899-7071/© 2014 Elsevier Inc. All rights reserved.
Please cite this article as: Zippel D, et al, Magnetic resonance imaging (MRI) evaluation of residual breast tissue following mastectomy and reconstruction with silicone implants, Clin Imaging (2015), http://dx.doi.org/10.1016/j.clinimag.2014.12.014
2
D. Zippel et al. / Clinical Imaging xxx (2015) xxx–xxx
reconstruction using silicone prosthesis, differentiating those patients undergoing mastectomy for carcinoma from those undergoing prophylactic mastectomy.
2. Materials and methods The analysis of this data was approved by the local hospital Institutional Review Board. A retrospective review of breast MR images was conducted at The Meirav Breast Center of the Chaim Sheba Medical Center, Ramat Gan, Israel, between January and November 2011 including women who had undergone mastectomy, with the patient list crosschecking hospital oncology, surgery, and radiology databases.
Breast MRI was performed on a 1.5-T (Signa Excite HDX, GE Healthcare) device with a dedicated double breast coil (eight channels) and a standard dynamic and implant bilateral breast MRI protocol. Dynamic contrast-enhanced T1-weighted a 3D axial vibrant multiphase with the following parameters [repetition time (TR)/echo time (TE) = 5.4/2.6; flip angle, 15; bandwidth, 83.3 kHz; matrix, 512×364; FOV = 340 mm; section thickness, 2 mm; no intersection gap]. Then, a bolus of contrast material (gadobutrol, Gadovist, Bayer Schering Pharma) was administered using an automated injector at 2 ml/s followed by a 20-ml saline flush at the same injection rate. The dose was adjusted, and 0.1 ml/kg of body weight was given. Thereafter, five contrast-enhanced axial vibrant multiphase series were performed. Subtraction images were obtained with the use of a software subtraction function. For implants, axial and sagittal fast spin-echo T2-weighted images with water suppression (TR/TE, 6000/80; slice thickness, 3 mm; matrix, 256×256; repetitions, 2; FOV, 16 cm) and axial inversion recovery T2weighted sequences with water suppression (3000/156; inversion time, 180 ms; echo-train length 16; slice thickness, 4 mm; matrix, 256×192; repetition, 1; FOV, 20 cm) were obtained through each breast separately. We then obtained axial fast spin-echo T2-weighted images with silicone suppression using the same parameters and slice selection. The residual breast thickness was evaluated at four points (3, 6, 9, and 12 o'clock positions) with a digital caliper assessing T2-weighted images in the measurement of RBT at the 3 and 9 o'clock positions (Fig. 1A) and sagittal T1-weighted images for measurements at the 6 and 12 o'clock positions (Fig. 1B). Patient data were collated from the combined electronic records of the different databases. 2.1. Statistics Statistical analysis was performed using STATA 12 SE (StataCorp.4905 Lakeway Drive, College Station, TX, USA). Data are presented as means ± standard deviations. Comparisons between the two groups were made using the Student’s t test. Monotone relationships between age and RBT was tested using Kendall tau and the Spearman rank correlation coefficient to demonstrate that the conclusion does not depend on the approach because these two approaches treated the data differently. Linear regression for panel data (considering a breast as a panel) of the residual on the direction was used to take into account the correlation of residuals within each breast of the same patient. Linear regression of RBT was used to assess the effect of age and year of mastectomy. Nonparametric LOWESS smoothing was used to present the effect of the year of mastectomy on measurable RBT. All tests were two-sided. P values b.05 were recorded as significant. 3. Results During the period of study, 45 women were evaluated where, overall, 88 breasts were examined. The mean age was 42.22±9.63 years (range, 26–61 years). Overall RBT width measured for the whole cohort was 11.17±6.02 mm. Comparisons were made of RBT between those patients undergoing mastectomy for carcinoma (group 1; n = 45) and Table 1 Mean width (mm), width range, and S.D. of RBT of the cohort measured at the different locales Locale 3 o'clock
Fig. 1. (A) A 52-year-old female with left-sided breast cancer. Axial T2-weighted image for measurements at the 3 and 9 o'clock positions. (B) A 52-year-old female with left-sided breast cancer. Sagittal T1-weighted images for measurements at the 6 and 12 o'clock positions.
6 o'clock
9 o'clock
12 o'clock
Minimum 0 2.1 0 1.3 Maximum 31.7 47.8 42.2 53.4 Mean 8.8 13.3 9.3 13.3 S.D. 5.6 9.6 6.1 11.0 Overall mean RBT: 11.17 mm Mean RBT group 1 (therapeutic): 10.63 mm; group 2 (prophylactic): 11.86 mm (P = .09)
Please cite this article as: Zippel D, et al, Magnetic resonance imaging (MRI) evaluation of residual breast tissue following mastectomy and reconstruction with silicone implants, Clin Imaging (2015), http://dx.doi.org/10.1016/j.clinimag.2014.12.014
D. Zippel et al. / Clinical Imaging xxx (2015) xxx–xxx
those undergoing prophylactic mastectomy (group 2; n = 43). Table 1 shows the mean width of RBT measured at the different locales. Both the minimum and maximum widths of RBT were least at the 3 and 9 o'clock positions, with greater minimum and maximum RBT values being recorded at the 6 and 12 o'clock locales. When comparing group 1 and group 2 cases, the mean width of RBT was smaller in group 1 cases (10.63±5.41 mm) when compared with group 2 patients (11.86 mm±6.77), although this difference did not reach statistical significance (P = .09). A positive correlation of the mean RBT was found with the operation date (Spearman rank correlation coefficient P = .046 and Kendall tau P = .036) and with age at operation (Spearman rank correlation coefficient P = .022 and Kendall tau P = .034). It means that the measured RBT increased with increasing age of the patient (Fig. 2) and also increased in later years (Fig. 3). The correlation between the year of operation and age at operation was highly significant (Pearson r = 0.34, P = .0013), meaning that the operations in later years were performed on elder patients. The linear regression of RBT on age and year of operation showed that the measured RBT increased with age [0.136±0.102 mm per year (P = .188)] and year of operation [.835±0.489 mm per year (P = .092)]. Linear regression of residuals on directions (considering a breast as a panel) showed that, as compared to direction 3, the average residuals in direction 6 was 4.46±1.27 mm bigger (P b .001); in direction 9, it was .55±1.27 mm bigger (P = .663); and in direction 12, it was 4.49±1.27 mm bigger (P b .001). 4. Discussion This study was undertaken to try to objectively quantify the amount of RBT after mastectomy and immediate reconstructive surgery. Variable thickness of RBT ranging from no visible tissue up to 53.4 mm is demonstrable following mastectomy and implant reconstruction using MRI, where the maximal thickness is evident in the superior part of the reconstructed breast and where the least amount of RBT is found at the medial or lateral margins. The results demonstrated that the residuals in vertical directions (6 and 12) were significantly greater than in horizontal directions (3 and 9). Although there was no statistical difference in the width of RBT between women undergoing mastectomy for cancer or as prophylaxis, smaller measurable widths of RBT were detected in the mastectomy group (group 1). Interestingly, with advancing age, more RBT remained after surgery, suggesting a tendency to more aggressive surgery in the young cancer patient. This is offset by the finding that, with a more recent date of surgery, there has been a trend to leave more RBT. Although beyond the scope of this study, it is intuitive that leaving more RBT in patients either undergoing mastectomy for cancer or as a
Fig. 2. Age-adjusted regression analysis showing increased RBT with patient age.
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Fig. 3. Increased RBT over time, as measured by year of operation.
prophylactic procedure would respectively be associated with a higher likelihood of local recurrence or would leave breast tissue which could subsequently undergo malignant transformation. It is suggested that a measurable amount of RBT may place patients in either category at increased risk for cancer development. The overall risk of locoregional recurrence after mastectomy is estimated at between 7% and 10% [18], suggesting that patients with a history even of bilateral mastectomy require continued surveillance for recurrence as well as for the development of a new primary breast cancer. The BRCA carrier patient poses a particular problem. A recent study has shown that, in BRCA carriers, even after mastectomy, there is an annual incidence of 0.8% of recurrent cancer, which underscores the clinical significance of RBT in very high risk patients [19]. Although there is enough evidence that MRI is the most suitable tool for screening of otherwise healthy BRCA mutation carriers [20], very little has been reported concerning the use of MRI as a surveillance or diagnostic tool in the mastectomized patient, where inherent biases for its use depend upon the nature of the radiological referral (oncologist, surgeon, or radiation specialist) as well as whether an MR was indicated for ancillary signs and symptoms (mass, evaluation of regional lymph nodes, or pain). In these clinical settings, the vast majority of MR examinations show benign imaging findings [8,9], although they may lead to derivative imaging investigations which are most commonly designed to evaluate lesions lying outside the residual breast region. When used for the detection of locoregional recurrence following mastectomy, MRI appears to add little to clinical examination, without any specific benefit as a surveillance tool [9]. While MRI can indeed distinguish between fat tissue and glandular tissue, following a subcutaneous dissection for mastectomy, the amount of glandular tissue as opposed to fat tissue will be at a minimum and under the resolution of an MRI. It is, however, anticipated that discovery of significant RBT would influence the use of an accurate surveillance modality like MRI, although the presence of RBT is frequently not mentioned in radiology reports. Where there is a suspicion of RBT, liaison between the referring clinician and the radiologist is required so that its presence and nature are included in the final report. The question of whether to consider some sort of adjuvant treatment such as radiation should the radiologist feel there is a significant amount of RBT in oncologic mastectomies may be something which warrants further investigation. The likelihood of RBT (as opposed to residual cancer) also depends upon the type of mastectomy performed, where skin sparing mastectomies have been associated with residual terminal ductal lobular units in the retained skin flap in up to half the cases [13,21]. More minimalist approaches attempting to preserve tissues in the inframmamary fold can leave breast tissue or intramammary lumph nodes in 28% of cases, questioning the safety of this type of technique [22]. Even with
Please cite this article as: Zippel D, et al, Magnetic resonance imaging (MRI) evaluation of residual breast tissue following mastectomy and reconstruction with silicone implants, Clin Imaging (2015), http://dx.doi.org/10.1016/j.clinimag.2014.12.014
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conventional modified radical mastectomy, up to 20% of patients may have residual glandular tissue at the anatomical mastectomy margins, representing up to 2% of the normal glandular volume of the resected breast [23]. In our study, more recent mastectomies were associated with more measurable RBT, suggesting that, although total mastectomy was the standard procedure performed, it is being conducted more conservatively. This is also a more conservative surgical resection feature of those patients undergoing prophylactic mastectomies where the RBT left is greater when compared with those mastectomized for cancer. In the few studies assessing the demographic risk factors for RBT following mastectomy, the likelihood of residual remaining glandular tissue is increased with the use of thicker skin flaps (exceeding 5 mm), without any clear association between RBT and the presence of denser breasts, younger or premenopausal women, or those with lower parity [13]. The technical ability to obtain the optimal dissection plane during mastectomy just in front of the superficial fascia of the breast may be limited, where Beer et al. showed that there was an absence of this demarcated fascial plane in nearly half of patients undergoing breast reduction surgery, particularly when the patient was obese [24]. In cases when this fascia was irregular, glandular tissue was seen to readily breach this plane, and this is a surgical feature contributing to the presence of RBT. Our study is limited by its retrospective and observational nature, with a possible selection bias in patient collection. Distinction needs to be made in the postmastectomy patient between MR use for the detection of possible recurrence or de novo cancer or for the estimation of RBT in a patient potentially at risk for cancer development. When specifically used for the detection of locoregional recurrence after mastectomy and its distinction from postsurgical scar and fat necrosis, MRI appears to be the best available modality [7]. Mastectomy patients are, however, a heterogeneous group, where it has been suggested by some that those with implants do not require imaging surveillance as recurrences are readily palpated because the posterior margin of the mastectomy bed is displaced anteriorly [25]. In those with flap reconstruction, the flap may obscure early detection of a chest wall recurrence where those with a higher risk of recurrence (based on tumor features or margin status) will require regular imaging surveillance [26]. Further limitation lies in the ability to distinguish glandular tissue (which is at risk of cancerous transformation) from fatty residuum. MRI and other imaging modalities cannot distinguish between fatty and fibroglandular tissue, which can only be assessed by histology. Additionally, the timing of the follow-up MRI examination will also influence the sensitivity of detection of abnormalities such as areas of fat necrosis, skin thickening, and seroma and hematoma formation which may morphologically resemble tumor recurrence, although these MR changes will diminish over time [27–29]. In summary, RBT, which is often not reported by radiologists, is demonstrable on MRI after a mastectomy and is most prominent in the upper part of the mastectomy bed. Its presence is more common when a conservative prophylactic mastectomy is performed, but it is unclear whether there is value in routine MR surveillance of those with RBT and a higher risk of locoregional recurrence or new primary cancer development. The increasing use of axial breast MRI to screen for cancer of the contralateral breast allows a view of the mastectomized side alongside the native breast, permitting an assessment of RBT as a potential marker for locally recurrent disease prior to clinical presentation.
Conflict of interest disclosure statement The authors declare that they have no conflict of interest.
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Please cite this article as: Zippel D, et al, Magnetic resonance imaging (MRI) evaluation of residual breast tissue following mastectomy and reconstruction with silicone implants, Clin Imaging (2015), http://dx.doi.org/10.1016/j.clinimag.2014.12.014
Contents lists available at ScienceDirect
Clinical Imaging journal homepage: http://www.clinicalimaging.org
Magnetic resonance imaging (MRI) evaluation of residual breast tissue following mastectomy and reconstruction with silicone implants Douglas Zippel a,e,⁎, Vered Tsehmaister-Abitbol b, Arie Rundstein b, Anat Shalmon b, Andrew Zbar a, Gil Nardini c, Ilya Novikov d, Miri Sklair-Levy b,e a
Department of Surgery, Chaim Sheba Medical Center, Tel Hashomer, Israel 52621 Department of Diagnostic Imaging, Chaim Sheba Medical Center, Tel Hashomer, Israel 52621 Department of Plastic Surgery, Chaim Sheba, Chaim Sheba Medical Center, Tel Hashomer, Israel 52621 d Gertner Institute for Epidemiology and Health Policy Research, Chaim Sheba Medical Center, Tel Hashomer, Israel 52621 e Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel b c
a r t i c l e
i n f o
Article history: Received 7 September 2014 Received in revised form 16 November 2014 Accepted 9 December 2014 Available online xxxx Keywords: Residual breast tissue Breast cancer Magnetic resonance imaging Breast reconstruction
a b s t r a c t Purpose: We present our use of magnetic resonance (MR) measurement to determine the amount of residual breast tissue (RBT) following total mastectomy with reconstruction. Methods: Breast MR images of 45 women who underwent surgery between January and November 2011 were reviewed. The cohort included therapeutic and prophylactic mastectomies. RBT was evaluated at four points with a digital caliper assessing T2-weighted and T1-weighted images. Results: Patients undergoing mastectomy for carcinoma tended to have less RBT than in prophylactic surgery. Greater age and recent surgery both correlated with larger RBT. Conclusions: Variable thickness of RBT is demonstrable following mastectomy and implant reconstruction using MR imaging. © 2014 Elsevier Inc. All rights reserved.
1. Introduction The use of mastectomy for the primary treatment of breast cancer has increased in recent years [1,2], as has the contralateral prophylactic mastectomy rate in those who have already undergone a prior mastectomy on one side [3]. In particular, with the increased awareness of the role of genetic mutations such as BRCA1 and BRCA2 in breast cancer especially in young women, the use of bilateral mastectomy, with or without immediate reconstruction, has been ever increasing [4]. The clinical issues concerning the use of magnetic resonance imaging (MRI) in such patients have centered on the critical role it plays in the delineation of the diagnosis of multifocal lesions which directly alters the surgical management and influences the mastectomy rate [5,6]. MRI has also been used to assess the reconstructed, mastectomized patient in order to detect locally recurrent disease [7,8]. In this latter setting, breast MRI accurately detects asymptomatic recurrence and defines the extent of disease, although little is currently known concerning its use as a surveillance tool after bilateral mastectomy [9].With the increasing use of bilateral breast MRI, the mastectomized side (reconstructed or not) is in-
⁎ Corresponding author. Department of Surgery, Chaim Sheba Medical Center, Tel Hashomer, Israel 52621. Tel.: +972 3 530 2714; fax: +972 3 534 1562. E-mail address: [email protected] (D. Zippel).
cluded in the field of view (FOV) and should not be dismissed under the assumption that there is no remaining residual breast tissue (RBT). The anatomic breast, although typically described as spanning the second to the sixth ribs, may extend to the clavicle superiorly, to the axilla superolaterally, to the oblique edge of the latissimus dorsi posteriorly, and to the costal margin inferiorly [10]. In addition, the breast may harbor a varying amount of glandular, adipose, and connective tissue, resulting in a wide degree of disparity between individuals. These inherent differences in breast composition, resulting in varying density, may influence the relative risk for carcinoma development [11]. The risk imposed for carcinoma development after a total mastectomy also depends upon the technique used. Skin-sparing mastectomy, which preserves the skin envelope surrounding the breast parenchyma, allows immediate breast reconstruction (IBR) with silicone implants. IBR decreases the requirement for secondary procedure in which surplus skin needs to be recruited using tissue expanders, results in improved body image and high levels of patient satisfaction as well as being oncologically sound [12], and leaves behind minimal RBT [13]. In theory, the amount of RBT will influence the relative risk for residual carcinoma development, although there are only five studies which have previously reported the rates of RBT following mastectomy [13–17]. We present our use of MR measurement to objectively determine the amount of RBT following total mastectomy with breast
http://dx.doi.org/10.1016/j.clinimag.2014.12.014 0899-7071/© 2014 Elsevier Inc. All rights reserved.
Please cite this article as: Zippel D, et al, Magnetic resonance imaging (MRI) evaluation of residual breast tissue following mastectomy and reconstruction with silicone implants, Clin Imaging (2015), http://dx.doi.org/10.1016/j.clinimag.2014.12.014
2
D. Zippel et al. / Clinical Imaging xxx (2015) xxx–xxx
reconstruction using silicone prosthesis, differentiating those patients undergoing mastectomy for carcinoma from those undergoing prophylactic mastectomy.
2. Materials and methods The analysis of this data was approved by the local hospital Institutional Review Board. A retrospective review of breast MR images was conducted at The Meirav Breast Center of the Chaim Sheba Medical Center, Ramat Gan, Israel, between January and November 2011 including women who had undergone mastectomy, with the patient list crosschecking hospital oncology, surgery, and radiology databases.
Breast MRI was performed on a 1.5-T (Signa Excite HDX, GE Healthcare) device with a dedicated double breast coil (eight channels) and a standard dynamic and implant bilateral breast MRI protocol. Dynamic contrast-enhanced T1-weighted a 3D axial vibrant multiphase with the following parameters [repetition time (TR)/echo time (TE) = 5.4/2.6; flip angle, 15; bandwidth, 83.3 kHz; matrix, 512×364; FOV = 340 mm; section thickness, 2 mm; no intersection gap]. Then, a bolus of contrast material (gadobutrol, Gadovist, Bayer Schering Pharma) was administered using an automated injector at 2 ml/s followed by a 20-ml saline flush at the same injection rate. The dose was adjusted, and 0.1 ml/kg of body weight was given. Thereafter, five contrast-enhanced axial vibrant multiphase series were performed. Subtraction images were obtained with the use of a software subtraction function. For implants, axial and sagittal fast spin-echo T2-weighted images with water suppression (TR/TE, 6000/80; slice thickness, 3 mm; matrix, 256×256; repetitions, 2; FOV, 16 cm) and axial inversion recovery T2weighted sequences with water suppression (3000/156; inversion time, 180 ms; echo-train length 16; slice thickness, 4 mm; matrix, 256×192; repetition, 1; FOV, 20 cm) were obtained through each breast separately. We then obtained axial fast spin-echo T2-weighted images with silicone suppression using the same parameters and slice selection. The residual breast thickness was evaluated at four points (3, 6, 9, and 12 o'clock positions) with a digital caliper assessing T2-weighted images in the measurement of RBT at the 3 and 9 o'clock positions (Fig. 1A) and sagittal T1-weighted images for measurements at the 6 and 12 o'clock positions (Fig. 1B). Patient data were collated from the combined electronic records of the different databases. 2.1. Statistics Statistical analysis was performed using STATA 12 SE (StataCorp.4905 Lakeway Drive, College Station, TX, USA). Data are presented as means ± standard deviations. Comparisons between the two groups were made using the Student’s t test. Monotone relationships between age and RBT was tested using Kendall tau and the Spearman rank correlation coefficient to demonstrate that the conclusion does not depend on the approach because these two approaches treated the data differently. Linear regression for panel data (considering a breast as a panel) of the residual on the direction was used to take into account the correlation of residuals within each breast of the same patient. Linear regression of RBT was used to assess the effect of age and year of mastectomy. Nonparametric LOWESS smoothing was used to present the effect of the year of mastectomy on measurable RBT. All tests were two-sided. P values b.05 were recorded as significant. 3. Results During the period of study, 45 women were evaluated where, overall, 88 breasts were examined. The mean age was 42.22±9.63 years (range, 26–61 years). Overall RBT width measured for the whole cohort was 11.17±6.02 mm. Comparisons were made of RBT between those patients undergoing mastectomy for carcinoma (group 1; n = 45) and Table 1 Mean width (mm), width range, and S.D. of RBT of the cohort measured at the different locales Locale 3 o'clock
Fig. 1. (A) A 52-year-old female with left-sided breast cancer. Axial T2-weighted image for measurements at the 3 and 9 o'clock positions. (B) A 52-year-old female with left-sided breast cancer. Sagittal T1-weighted images for measurements at the 6 and 12 o'clock positions.
6 o'clock
9 o'clock
12 o'clock
Minimum 0 2.1 0 1.3 Maximum 31.7 47.8 42.2 53.4 Mean 8.8 13.3 9.3 13.3 S.D. 5.6 9.6 6.1 11.0 Overall mean RBT: 11.17 mm Mean RBT group 1 (therapeutic): 10.63 mm; group 2 (prophylactic): 11.86 mm (P = .09)
Please cite this article as: Zippel D, et al, Magnetic resonance imaging (MRI) evaluation of residual breast tissue following mastectomy and reconstruction with silicone implants, Clin Imaging (2015), http://dx.doi.org/10.1016/j.clinimag.2014.12.014
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those undergoing prophylactic mastectomy (group 2; n = 43). Table 1 shows the mean width of RBT measured at the different locales. Both the minimum and maximum widths of RBT were least at the 3 and 9 o'clock positions, with greater minimum and maximum RBT values being recorded at the 6 and 12 o'clock locales. When comparing group 1 and group 2 cases, the mean width of RBT was smaller in group 1 cases (10.63±5.41 mm) when compared with group 2 patients (11.86 mm±6.77), although this difference did not reach statistical significance (P = .09). A positive correlation of the mean RBT was found with the operation date (Spearman rank correlation coefficient P = .046 and Kendall tau P = .036) and with age at operation (Spearman rank correlation coefficient P = .022 and Kendall tau P = .034). It means that the measured RBT increased with increasing age of the patient (Fig. 2) and also increased in later years (Fig. 3). The correlation between the year of operation and age at operation was highly significant (Pearson r = 0.34, P = .0013), meaning that the operations in later years were performed on elder patients. The linear regression of RBT on age and year of operation showed that the measured RBT increased with age [0.136±0.102 mm per year (P = .188)] and year of operation [.835±0.489 mm per year (P = .092)]. Linear regression of residuals on directions (considering a breast as a panel) showed that, as compared to direction 3, the average residuals in direction 6 was 4.46±1.27 mm bigger (P b .001); in direction 9, it was .55±1.27 mm bigger (P = .663); and in direction 12, it was 4.49±1.27 mm bigger (P b .001). 4. Discussion This study was undertaken to try to objectively quantify the amount of RBT after mastectomy and immediate reconstructive surgery. Variable thickness of RBT ranging from no visible tissue up to 53.4 mm is demonstrable following mastectomy and implant reconstruction using MRI, where the maximal thickness is evident in the superior part of the reconstructed breast and where the least amount of RBT is found at the medial or lateral margins. The results demonstrated that the residuals in vertical directions (6 and 12) were significantly greater than in horizontal directions (3 and 9). Although there was no statistical difference in the width of RBT between women undergoing mastectomy for cancer or as prophylaxis, smaller measurable widths of RBT were detected in the mastectomy group (group 1). Interestingly, with advancing age, more RBT remained after surgery, suggesting a tendency to more aggressive surgery in the young cancer patient. This is offset by the finding that, with a more recent date of surgery, there has been a trend to leave more RBT. Although beyond the scope of this study, it is intuitive that leaving more RBT in patients either undergoing mastectomy for cancer or as a
Fig. 2. Age-adjusted regression analysis showing increased RBT with patient age.
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Fig. 3. Increased RBT over time, as measured by year of operation.
prophylactic procedure would respectively be associated with a higher likelihood of local recurrence or would leave breast tissue which could subsequently undergo malignant transformation. It is suggested that a measurable amount of RBT may place patients in either category at increased risk for cancer development. The overall risk of locoregional recurrence after mastectomy is estimated at between 7% and 10% [18], suggesting that patients with a history even of bilateral mastectomy require continued surveillance for recurrence as well as for the development of a new primary breast cancer. The BRCA carrier patient poses a particular problem. A recent study has shown that, in BRCA carriers, even after mastectomy, there is an annual incidence of 0.8% of recurrent cancer, which underscores the clinical significance of RBT in very high risk patients [19]. Although there is enough evidence that MRI is the most suitable tool for screening of otherwise healthy BRCA mutation carriers [20], very little has been reported concerning the use of MRI as a surveillance or diagnostic tool in the mastectomized patient, where inherent biases for its use depend upon the nature of the radiological referral (oncologist, surgeon, or radiation specialist) as well as whether an MR was indicated for ancillary signs and symptoms (mass, evaluation of regional lymph nodes, or pain). In these clinical settings, the vast majority of MR examinations show benign imaging findings [8,9], although they may lead to derivative imaging investigations which are most commonly designed to evaluate lesions lying outside the residual breast region. When used for the detection of locoregional recurrence following mastectomy, MRI appears to add little to clinical examination, without any specific benefit as a surveillance tool [9]. While MRI can indeed distinguish between fat tissue and glandular tissue, following a subcutaneous dissection for mastectomy, the amount of glandular tissue as opposed to fat tissue will be at a minimum and under the resolution of an MRI. It is, however, anticipated that discovery of significant RBT would influence the use of an accurate surveillance modality like MRI, although the presence of RBT is frequently not mentioned in radiology reports. Where there is a suspicion of RBT, liaison between the referring clinician and the radiologist is required so that its presence and nature are included in the final report. The question of whether to consider some sort of adjuvant treatment such as radiation should the radiologist feel there is a significant amount of RBT in oncologic mastectomies may be something which warrants further investigation. The likelihood of RBT (as opposed to residual cancer) also depends upon the type of mastectomy performed, where skin sparing mastectomies have been associated with residual terminal ductal lobular units in the retained skin flap in up to half the cases [13,21]. More minimalist approaches attempting to preserve tissues in the inframmamary fold can leave breast tissue or intramammary lumph nodes in 28% of cases, questioning the safety of this type of technique [22]. Even with
Please cite this article as: Zippel D, et al, Magnetic resonance imaging (MRI) evaluation of residual breast tissue following mastectomy and reconstruction with silicone implants, Clin Imaging (2015), http://dx.doi.org/10.1016/j.clinimag.2014.12.014
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conventional modified radical mastectomy, up to 20% of patients may have residual glandular tissue at the anatomical mastectomy margins, representing up to 2% of the normal glandular volume of the resected breast [23]. In our study, more recent mastectomies were associated with more measurable RBT, suggesting that, although total mastectomy was the standard procedure performed, it is being conducted more conservatively. This is also a more conservative surgical resection feature of those patients undergoing prophylactic mastectomies where the RBT left is greater when compared with those mastectomized for cancer. In the few studies assessing the demographic risk factors for RBT following mastectomy, the likelihood of residual remaining glandular tissue is increased with the use of thicker skin flaps (exceeding 5 mm), without any clear association between RBT and the presence of denser breasts, younger or premenopausal women, or those with lower parity [13]. The technical ability to obtain the optimal dissection plane during mastectomy just in front of the superficial fascia of the breast may be limited, where Beer et al. showed that there was an absence of this demarcated fascial plane in nearly half of patients undergoing breast reduction surgery, particularly when the patient was obese [24]. In cases when this fascia was irregular, glandular tissue was seen to readily breach this plane, and this is a surgical feature contributing to the presence of RBT. Our study is limited by its retrospective and observational nature, with a possible selection bias in patient collection. Distinction needs to be made in the postmastectomy patient between MR use for the detection of possible recurrence or de novo cancer or for the estimation of RBT in a patient potentially at risk for cancer development. When specifically used for the detection of locoregional recurrence after mastectomy and its distinction from postsurgical scar and fat necrosis, MRI appears to be the best available modality [7]. Mastectomy patients are, however, a heterogeneous group, where it has been suggested by some that those with implants do not require imaging surveillance as recurrences are readily palpated because the posterior margin of the mastectomy bed is displaced anteriorly [25]. In those with flap reconstruction, the flap may obscure early detection of a chest wall recurrence where those with a higher risk of recurrence (based on tumor features or margin status) will require regular imaging surveillance [26]. Further limitation lies in the ability to distinguish glandular tissue (which is at risk of cancerous transformation) from fatty residuum. MRI and other imaging modalities cannot distinguish between fatty and fibroglandular tissue, which can only be assessed by histology. Additionally, the timing of the follow-up MRI examination will also influence the sensitivity of detection of abnormalities such as areas of fat necrosis, skin thickening, and seroma and hematoma formation which may morphologically resemble tumor recurrence, although these MR changes will diminish over time [27–29]. In summary, RBT, which is often not reported by radiologists, is demonstrable on MRI after a mastectomy and is most prominent in the upper part of the mastectomy bed. Its presence is more common when a conservative prophylactic mastectomy is performed, but it is unclear whether there is value in routine MR surveillance of those with RBT and a higher risk of locoregional recurrence or new primary cancer development. The increasing use of axial breast MRI to screen for cancer of the contralateral breast allows a view of the mastectomized side alongside the native breast, permitting an assessment of RBT as a potential marker for locally recurrent disease prior to clinical presentation.
Conflict of interest disclosure statement The authors declare that they have no conflict of interest.
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Please cite this article as: Zippel D, et al, Magnetic resonance imaging (MRI) evaluation of residual breast tissue following mastectomy and reconstruction with silicone implants, Clin Imaging (2015), http://dx.doi.org/10.1016/j.clinimag.2014.12.014
