Trends and variations in postmastectomy radiation therapy for breast cancer in patients with 1 to 3 positive lymph nodes: A National Cancer Data Base analysis

Assessment of Postmastectomy Radiation Therapy Receipt by Age and Association With Outcomes in Women With Breast Cancer

PURPOSE

Postmastectomy radiation therapy (PMRT) reduces locoregional recurrence (LRR) and improves overall survival (OS) in patients with breast cancer. Young age has been recognized as a risk factor for LRR. The primary objective of this study was to determine if recommendations for PMRT differed among patients younger than 50 years as compared to women aged 50 years or older.

METHODS

We reviewed medical records of patients with breast cancer who underwent mastectomy with or without PMRT from 2010 through 2018. Univariable and multivariable models were used to estimate the association of age with PMRT.

RESULTS

Of 2471 patients, 839 (34%) were <50 years; 1632 (66%) were ≥50 years. Patients <50 years had a higher percentage of grade 3 tumors, hormone receptor (HR) negative and/or Her-2/neu positive tumors, clinical stage T2/T3 tumors, and nodal involvement. Compared with patients ≥50 years, patients <50 years were more likely to undergo PMRT (OR 1.57; P = .001) and regional node irradiation (RNI) to the internal mammary nodes. Advanced clinical and pathologic stage, invasive tumor histology, the presence of lymphovascular invasion, and treatment with systemic chemotherapy were predictors of PMRT receipt for patients <50 years (P < .05). PMRT was associated with improved OS and recurrence free survival (RFS) among all patients (P < .01).

CONCLUSION

Patients <50 years were more likely to undergo PMRT and to receive RNI to the internal mammary nodes but were also more likely to have other risk factors for recurrence that would warrant a PMRT recommendation. PMRT improved OS and RFS for all patients.

Variation in Rates of Post-Mastectomy Radiotherapy Among Women with Early Invasive Breast Cancer in England and Wales: A Population-Based Cohort Study

AIMS

This study examined whether patterns of post-mastectomy radiotherapy (PMRT) among women with early invasive breast cancer (EIBC) varied within England and Wales and explored the role of different patient factors in explaining any variation.

MATERIALS AND METHODS

The study used national cancer data on women aged ≥50 years diagnosed with EIBC (stage I-IIIa) in England and Wales between January 2014 and December 2018 who had a mastectomy within 12 months of diagnosis. A multilevel mixed-effects logistic regression model was used to calculate risk-adjusted rates of PMRT for geographical regions and National Health Service acute care organisations. The study examined the variation in these rates within subgroups of women with different risks of recurrence (low: T1-2N0; intermediate: T3N0/T1-2N1; high: T1-2N2/T3N1-2) and investigated whether the variation was linked to patient case-mix within regions and organisations.

RESULTS

Among 26 228 women, use of PMRT increased with greater recurrence risk (low: 15.0%; intermediate: 59.4%; high: 85.1%). In all risk groups, use of PMRT was more common among women who had received chemotherapy and decreased among women aged ≥80 years. There was weak or no evidence of an association between use of PMRT and comorbidity or frailty, for each risk group. In women with an intermediate risk, unadjusted rates of PMRT varied substantially between geographical regions (range 40.3-77.3%), but varied less for the high-risk (range 77.1-91.6%) and low-risk groups (range 4.1-32.9%). Adjusting for patient case-mix reduced the variation in regional and organisational PMRT rates to a small degree.

CONCLUSIONS

Rates of PMRT are consistently high across England and Wales among women with high-risk EIBC, but variation exists across regions and organisations for women with intermediate-risk EIBC. Effort is required to reduce unwarranted variation in practice for intermediate-risk EIBC.

Factors Associated with Reconstruction Failure and Major Complications After Postmastectomy Radiation to a Reconstructed Breast

PURPOSE

Postmastectomy radiation therapy is known to increase risk of complications in the reconstruction setting. We aim to identify the variables associated with reconstruction failure and other major complications.

METHODS AND MATERIALS

A prospectively collected institutional database was queried for patients with up to stage IIIC breast cancer treated from 2000 to 2017, undergoing mastectomy, immediate implant or autologous tissue reconstruction, and radiation to the reconstructed breast within 1 year of surgery. Reconstruction failure was defined as complication requiring surgical revision or implant removal. Additional major complications were defined as any infection, contracture, necrosis, or fibrosis. Covariates of interest included age, body mass index, smoking status, stage, hormone receptor and HER2 status, systemic therapy timing, radiation technique, nodal irradiation, and interval between surgery and start of postmastectomy radiation therapy. Differences in complication rates were assessed with χ² or Fisher exact tests. Competing risk regression was used to estimate hazard ratios; covariates were included one at a time to avoid over adjustment.

RESULTS

A total of 206 reconstructed breasts in 202 patients resulted from our initial query, with 139 treated with intensity-modulated radiation therapy (IMRT) and 67 treated with conventional radiation therapy (CRT). Median follow-up was 45 months (range, 4-210 months); patient cohorts were generally similar. Eight patients were excluded from toxicity analysis for insufficient follow-up (<2 years). Overall, reconstruction failure and major complication rates were significantly lower in the IMRT group. Reconstruction failure rates were 3.0% for IMRT versus 16.4% for CRT (P = .002), and major complication rates were 6.8% for IMRT versus 24.6% for CRT (P < .001). On univariate analysis, CRT was significantly predictive of implant failure (hazard ratio, 5.54; P = .003) and increased complication rates (hazard ratio, 3.83; P = .001). Significance persisted on multivariable analysis. Survival outcomes were similar, with no difference in 2 year overall survival (P = .12) and local recurrence (P = .41).

CONCLUSIONS

Using IMRT may improve reconstruction outcomes over CRT, with significantly lower reconstruction failure and complication rates without compromising local control or survival.

Delayed-immediate breast reconstruction: An assessment of complications and outcomes in the context of anticipated post-mastectomy radiotherapy

INTRODUCTION

The detrimental effects of post-mastectomy radiotherapy on breast reconstruction are well known. We report our experience with a delayed-immediate approach involving an initial subcutaneous implant with definitive reconstruction after adjuvant radiotherapy.

METHODS

Patients were identified retrospectively from hospital, theatre and implant registry records. Details regarding demographics, cancer pathology, surgical data and oncological therapies were collected. Primary outcomes included complication rates of first-stage surgery and time to definitive reconstruction.

RESULTS

A total of 115 patients underwent mastectomy and temporary subcutaneous implant (36 nipple sparing) between 2008 and 2019. Five were smokers with eleven having a body mass index > 30. The median age was 46 years (27-76 years) and tumour size 50 mm. Almost 95% underwent radiotherapy, 82% chemotherapy and 70% had axillary node clearance. Median mastectomy weight was 464 g (123-1300 g) with median temporary implant volume 375 cc (180-655 cc). Complications of first-stage surgery at three months included 5.2% implant loss (n = 6), 14.8% infection rate, 17.4% readmission rate and 10.4% returned to theatre. Reconstructive failure occurred in four cases (3.5%). A total of 76 patients completed definitive reconstruction, including 26 autologous, 21 latissimus dorsi with implant, and 28 implant-only reconstructions. The median time to reconstruction following the completion of radiotherapy was 12 months. This increased in those who had implant complications (28 vs. 15 months) or radiotherapy (16 vs. 10 months) versus those without.

CONCLUSIONS

Delayed-immediate breast reconstruction using a temporary subcutaneous implant has been shown to be a safe, feasible and potentially beneficial method than simple mastectomy and delayed reconstruction with a complication rate comparable to that of immediate implant reconstruction.

Omission of Intraoperative Frozen Section May Reduce Axillary Overtreatment Among Clinically Node-Negative Patients Having Upfront Mastectomy

BACKGROUND

The growing use of postmastectomy radiation/regional nodal irradiation (PMRT) has resulted in many women receiving both axillary dissection (ALND) and PMRT, increasing lymphedema rates. After developing standardized PMRT criteria, we adopted a policy of ALND omission among cN0 patients with 1-2 positive sentinel nodes (+SLNs) requiring PMRT. We evaluated how often overtreatment with ALND+PMRT was avoided with this approach.

METHODS

A retrospective review of a prospectively maintained database was performed beginning 1 year before policy adoption. Intraoperative SLN evaluation was routine pre- and post-policy. ALND was performed for SLN macrometastasis pre-policy, and selectively performed post-policy for 1-2 +SLNs based on PMRT criteria. ALND+PMRT was required for ≥ 3 +SLNs.

RESULTS

From March 1, 2018 to November 30, 2020, a total of 2207 cT1-3N0 patients had mastectomy and 231 had +SLNs; 109 (47%) were treated pre-policy and 122 (53%) post-policy. Most (81%) had 1-2 +SLNs. There was no change in rates of ALND+PMRT (64% pre-policy vs. 58% post-policy, p = 0.09), including in patients with 1-2 +SLNs (61% vs. 51%, p = 0.20). Post-policy, ALND was omitted in 9 (7%) patients recognized intraoperatively as PMRT candidates; avoidable ALND was performed in 40 (33%) patients not identified as PMRT candidates until receipt of final pathology. Overall, had intraoperative SLN evaluation been deferred, only 5.7% of patients would have required completion ALND: 2.2% (n = 49/2207) for ≥ 3 +SLNs and 3.5% (n = 77/2207) for 1-2 +SLNs without PMRT indication.

CONCLUSIONS

Most patients could have avoided ALND+PMRT if decision making was deferred until final pathology was available. Selective intraoperative SLN evaluation in cN0 patients having upfront mastectomy may reduce avoidable overtreatment.

Prepectoral breast reconstruction is safe in the setting of post-mastectomy radiation therapy

BACKGROUND

Many breast reconstruction patients undergo post-mastectomy radiation therapy (PMRT), which is well known to increase the risk of complications. There is limited data on outcomes and safety of prepectoral breast reconstruction in this setting. The purpose of this study was to compare the outcomes of prepectoral versus subpectoral two-stage breast reconstruction in patients undergoing PMRT.

METHODS

We conducted a retrospective cohort study of two-stage breast reconstructions performed at our institution during a 22-month period. Patients who received PMRT were identified, and two cohorts were created: those who underwent prepectoral versus subpectoral reconstruction. We collected data including patient characteristics, operative variables, and clinical outcomes. Bivariate analyses and multivariable logistic regressions were conducted.

RESULTS

We captured 313 patients (492 breasts) that had undergone two-stage reconstruction. A total of 69 breasts received PMRT; 28 were reconstructed prepectorally, and 41 breasts subpectorally. The two cohorts were well matched. We detected no differences in clinical outcomes between the two groups after a median follow-up time of 24 months. There, however, were differences in perioperative variables. Prepectoral reconstruction was associated with a shorter operative time, shorter length of hospital stay, higher cost, and shorter time to final reconstruction. Multivariable logistic regression demonstrated that prepectoral reconstruction is not an independent predictor of adverse events.

CONCLUSIONS

Although radiation is a known risk factor for many complications following breast reconstruction, prepectoral device placement is safe in this high-risk population. Although the rate of capsular contracture is reported to be higher in the general prepectoral population, this was not found in our radiated prepectoral population.

Contemporary Cancer Program Practice Profile Report (CP3R) Compliance Rates for Breast Cancer: A National Cancer Database Analysis

INTRODUCTION

The Commission on Cancer (CoC) issues Cancer Program Practice Profile Reports (CP3R) that set standards for high-quality care. Three metrics for breast cancer include radiation within 1 year for women < 70 years of age receiving breast-conserving surgery, radiation within 1 year after mastectomy for women with four or more positive lymph nodes (MASTRT), and hormonal therapy within 1 year of a stage IB-III hormone receptor-positive breast cancer (HT). Our study evaluates national trends in quality metric compliance.

METHODS

The National Cancer Database was queried from 2004 to 2014 to identify patients who met the criteria for the three quality metrics. National trends in compliance were compared.

RESULTS

Overall, 1,094,264 patients qualified for BCSRT (n = 534,147), MASTRT (n = 66,291), or HT (n = 493,826). In 2014, 91.1% of patients met BCSRT, 88.4% met MASTRT, and 90.7% met HT. BCSRT, MASTRT, and HT compliance rates were lower in community hospitals compared with Integrated Network Cancer Programs (INCP) (BCSRT: 89.0% vs. 92.8%, p < 0.01; MASTRT: 85.5% vs. 90.6%, p < 0.01; HT: 87.3% vs. 93.7%, p < 0.01). On multivariate analysis, patients receiving care at an INCP facility [odds ratio (OR) 1.47, 95% confidence interval (CI) 1.37-1.58] and insured patients (OR 1.70, 95% CI 1.54-1.87) had higher odds of BCSRT compliance, and minorities (OR 0.76, 95% CI 0.73-0.80) had lower odds. Similar results were seen for MASTRT and HT.

CONCLUSION

In more recent years, overall compliance rates for breast cancer quality metrics of BCSRT and HT by Comprehensive Community Cancer Programs, Academic/Research Programs, and INCPs have increased to meet the 90% CoC standards, while MASTRT has regressed. Community programs were least compliant with meeting the CoC standards.

Comparing complications in irradiated and non-irradiated free-flaps in patients with bilateral immediate breast reconstruction and unilateral post-mastectomy radiotherapy

BACKGROUND

Numerous studies have evaluated the effect of post-mastectomy radiotherapy (PMRT) on autologous breast reconstruction, but the variability of PMRT regimens and inadequate controls have made results difficult to interpret. Therefore, in this study, irradiated free-flaps are compared to non-irradiated internal controls in patients who underwent immediate bilateral reconstruction followed by unilateral PMRT to better delineate the effect of PMRT. The role of regional nodal irradiation (RNI) is also specifically assessed.

METHODS

Appropriate patients were identified through retrospective review. Complications such as fat necrosis, fibrosis, infection, delayed healing, and flap loss, as well as revision surgeries, among the irradiated free-flaps were compared to those on the contralateral non-irradiated side. Additional analyses were performed to evaluate the effect of patient demographics and treatment characteristics, such as RNI, on complications involving the irradiated free-flaps.

RESULTS

Seventy-three women were included. There was no significant difference between complication rates for the irradiated and non-irradiated free-flaps (39.7% vs. 38.4%, p = .78), although irradiated free-flaps were more likely to have fibrosis (17.0% vs. 0.0%; p < .0001) and multiple complications (9.6% vs. 0.0%; p = .02). Both groups underwent a similar number of revision surgeries (42.5% vs. 41.1%; p = .29). Looking at the irradiated free-flaps, internal mammary node (IMN) irradiation was the only factor predictive of complications (IRR 3.80, CI 1.32-10.97; p = .01).

CONCLUSIONS

PMRT may contribute to free-flap fibrosis, but does not appear to affect the overall risk of complications or revision surgeries. However, additional counseling is warranted if IMN irradiation is likely, as it is potentially associated with increased complications.

Arm Morbidity After Local Therapy for Young Breast Cancer Patients

BACKGROUND

The impact of patient demographics and local therapy choice on arm morbidity in young breast cancer patients is understudied despite its importance given the long survivorship period. This study assessed patient-reported arm morbidity in the Young Women's Breast Cancer Study (YWS), a prospective cohort study.

METHODS

From 2006 to 2016, 1302 women with breast cancer diagnosed at the age of 40 years or younger enrolled in the YWS. The participants regularly complete surveys. The response rates are higher than 86%. Using the Breast Cancer Prevention Trial Checklist, this study examined the prevalence of patient-reported postoperative arm swelling and decreased range of motion (ROM) 1 year after diagnosis, stratified by local therapy strategy, in patients who had surgery for stages 1 to 3 disease. Logistic regression analysis was used to identify risk factors for arm morbidity.

RESULTS

Among 888 eligible participants (median age, 37 years), 14% reported arm swelling and 34% reported decreased ROM at 1 year. Arm swelling was reported by 23.6% of the patients who had axillary lymph node dissection (ALND) and 24.6% of the patients who received ALND and post-mastectomy radiation therapy (PMRT). In the multivariable analysis, the patients who reported being financially uncomfortable or who had ALND were at higher risk of arm swelling at 1 year. Being overweight, receiving ALND after sentinel lymph node biopsy, and receiving PMRT were associated with decreased ROM at 1 year.

CONCLUSION

High rates of self-reported arm morbidity in young breast cancer survivors were reported, particularly in patients receiving ALND and PMRT. Attention to the risks and benefits of differing local therapy strategies for ALND and PMRT patients is warranted.

Impact of Postmastectomy Radiotherapy on Locoregional Control and Disease-Free Survival in Patients with Breast Cancer Treated with Neoadjuvant Chemotherapy

Background

The impact of postmastectomy radiotherapy (PMRT) in patients receiving neoadjuvant chemotherapy (NAC) is unclear. The purpose of this study is to identify the patients who may benefit from PMRT.

Methods

We retrospectively analysed patients with clinical stage II-III breast cancer who underwent NAC and modified radical mastectomy at our centre from 2007 to 2015. We investigated the relationship amongst locoregional recurrence rate (LRR), disease-free survival (DFS), and clinical pathological characters.

Results

A total of 554 patients were analysed in this study. The median follow-up time was 65 months. Amongst the patients, 58 (10.5%) had locoregional recurrence, 138 (24.9%) had distant metastasis, and 72 (13.0%) patients died. The 5-year cumulative incidence of LRR and DFS was 9.2% and 74.2%, respectively. A total of 399 (72%) patients received PMRT and 155 (28%) did not. The 5-year LRR of the patients with PMRT (7.3% vs. 14.1%, P=0.01) decreased significantly. We found that PMRT was an independent prognostic factor of LRR and DFS. Patients with the persistent involvement of 1–3 lymph nodes (ypN1) and more than 4 positive lymph nodes (ypN2-3) had a better outcome after PMRT than those without. However, the LRR and DFS of patients with negative lymph nodes at the time of surgery (ypN0) and who received PMRT showed no significant benefits. Amongst all patients with the three molecular subtypes of breast cancer, patients with triple-negative breast cancer had the highest pathological complete response rate but the worst prognosis (P=0.001).

Conclusion

Results showed that PMRT significantly reduced the LRR of patients with clinical stage II-III breast cancer after receiving NAC and mastectomy. YpN0 patients derived no local control or survival benefit after receiving PMRT, whereas those with ypN1 and ypN2-3 could obviously benefit from PMRT.

Quantifying the Impact of Axillary Surgery and Nodal Irradiation on Breast Cancer-Related Lymphedema and Local Tumor Control: Long-Term Results From a Prospective Screening Trial

PURPOSE

To independently evaluate the impact of axillary surgery type and regional lymph node radiation (RLNR) on breast cancer-related lymphedema (BCRL) rates in patients with breast cancer.

PATIENTS AND METHODS

From 2005 to 2018, 1,815 patients with invasive breast cancer were enrolled in a lymphedema screening trial. Patients were divided into the following 4 groups according to axillary surgery approach: sentinel lymph node biopsy (SLNB) alone, SLNB+RLNR, axillary lymph node dissection (ALND) alone, and ALND+RLNR. A perometer was used to objectively assess limb volume. All patients received baseline preoperative and follow-up measurements after treatment. Lymphedema was defined as a ≥ 10% relative increase in arm volume arising > 3 months postoperatively. The primary end point was the BCRL rate across the groups. Secondary end points were 5-year locoregional control and disease-free-survival.

RESULTS

The cohort included 1,340 patients with SLNB alone, 121 with SLNB+RLNR, 91 with ALND alone, and 263 with ALND+RLNR. The overall median follow-up time after diagnosis was 52.7 months for the entire cohort. The 5-year cumulative incidence rates of BCRL were 30.1%, 24.9%, 10.7%, and 8.0% for ALND+RLNR, ALND alone, SLNB+RLNR, and SLNB alone, respectively. Multivariable Cox models adjusted for age, body mass index, surgery, and reconstruction type showed that the ALND-alone group had a significantly higher BCRL risk (hazard ratio [HR], 2.66; P = .02) compared with the SLNB+RLNR group. There was no significant difference in BCRL risk between the ALND+RLNR and ALND-alone groups (HR, 1.20; P = .49) and between the SLNB-alone and SLNB+RLNR groups (HR, 1.33; P = .44). The 5-year locoregional control rates were similar for the ALND+RLNR, ALND-alone, SLNB+RLNR, and SLNB-alone groups (2.8%, 3.8%, 0%, and 2.3%, respectively).

CONCLUSION

Although RLNR adds to the risk of lymphedema, the main risk factor is the type of axillary surgery used.

Evaluation of capsular contracture following immediate prepectoral versus subpectoral direct-to-implant breast reconstruction

Capsular contracture is a common adverse outcome following implant breast reconstruction, often associated with radiation treatment. The authors hypothesize that muscle fibrosis is the main contributor of breast reconstruction contracture after radiation. Retrospective chart review identified patients that underwent DTI reconstruction with pre-or post-operative breast irradiation. Signs of capsular contracture were assessed using clinic notes and independent graders reviewing two-dimensional images and anatomic landmarks. Capsular contracture rate was greater in the subpectoral vs. prepectoral group (n = 28, 51.8% vs. n = 12, 30.0%, p = 0.02). When compared to prepectoral DTI reconstruction in irradiated patients, subpectoral implant placement was nearly 4 times as likely to result in capsular contracture (p < 0.01). Rates of explantation, infection, tissue necrosis, and hematoma were comparable between groups. We also found that when subpectoral patients present with breast contracture, chemoparalysis of the muscle alone can resolve breast asymmetry, corroborating that muscle is a key contributor to breast contracture. As prepectoral breast reconstruction is gaining popularity, there have been questions regarding outcome following radiation treatment. This study suggest that prepectoral breast reconstruction is safe in an irradiated patient population, and in fact compares favorably with regard to breast contracture.

Factors Leading to Decreased Rates of Immediate Postmastectomy Reconstruction

BACKGROUND

This study was performed to determine if there was a difference in immediate breast reconstruction (IBR) rates between our public hospital and private cancer center, which share a common faculty with a consistent management philosophy in multidisciplinary care. We investigated the factors affecting postmastectomy reconstruction and IBR rates.

MATERIALS AND METHODS

We retrospectively identified women with clinical stage I-II breast cancer who underwent mastectomy at our public hospital, Los Angeles County Medical Center, and our private cancer center, Keck Hospital of USC/Norris Comprehensive Cancer Center. Univariate and multivariate analyses were performed to study predictors of IBR and any breast reconstruction.

RESULTS

Of 293 mastectomy patients, the rate of any breast reconstruction at the private cancer (56.6%) center was higher than that at the public hospital (36.2%). IBR rates for the private cancer center (93.6%) and for patients with private insurance were higher than for the public hospital (40.8%) and likewise for those without insurance (86.7% versus 45.5%). In a multivariate analysis, the odds of IBR at our private cancer center were 22.96 times higher than that at our public hospital. Age >50 y and radiotherapy were independent predictive factors associated with less likelihood of any breast reconstruction.

CONCLUSIONS

Patients at the public hospital had a much lower rate of breast reconstruction than the private cancer center patients, even after controlling for stage and the team of treating physicians. Our results showed that older age and radiotherapy affect rates of breast reconstruction, as do hospital system and insurance status.

A 3-Dimensional Mapping Analysis of Regional Nodal Recurrences in Breast Cancer

PURPOSE

The primary goal was to map the anatomic pattern of isolated nodal recurrences (NR) in the supraclavicular (SCV), axillary, and internal mammary nodes (IMNs) in patients with breast cancer treated with curative-intent surgery with or without radiation therapy (RT). Secondary objectives were to assess clinical and pathologic factors associated with patterns of NR and survival rates.

METHODS AND MATERIALS

Patients with NR after treatment at a single cancer center during 1998 to 2013 were identified. Patients with prior distant metastases or NR without correlative imaging were excluded. All NRs were overlaid onto representative axial computed tomographic images. Multivariable analysis was performed to identify clinical and pathologic characteristics associated with NR. Kaplan-Meier curves were generated to assess the rate of relapse by nodal region according to pathologic feature or radiation treatment status.

RESULTS

The locations of 243 NRs among 153 eligible patients were mapped. The majority of NR occurred in the axilla (42%; 102/243), followed by the IMN (32.5%; 79/243) and the SCV (25.5%; 62/243). Radiation Therapy Oncology Group (RTOG) or European Society for Radiation therapy and Oncology (ESTRO) clinical target volume encompassed 82% (198/243) of NRs. The majority of out-of-field NRs were located in the lateral and posterior SCV region for both RTOG (67%; 30/45) and ESTRO (89%; 49/55) guidelines. The high-risk patients who received regional RT to the SCV relapsed at a similar rate in the medial, but a higher rate in lateral SCV (P = .009), compared with low-risk patients who received no nodal RT. Lymphovascular invasion most strongly associated with IMN NR (P = .001); grade 3 disease highly associated with both IMN (P = .001) and SCV NR (P = .02). The presence of an IMN NR portended for significantly inferior overall survival (OS), compared with an axillary NR, with a 5-year OS of 59% versus 72%, respectively (P = .03).

CONCLUSIONS

In this 3-dimensional image-based analysis of NR patterns in breast cancer patients treated with contemporary therapies, the lateral and posterior SCV represented a distinct site of NR that is not routinely included within current breast cancer contouring atlases. Grade 3 breast cancer and LVI were most commonly associated with the development of NR in the SCV. Modifying the CTV to encompass the lateral and posterior SCV in patients with breast cancer with these features might be justified.