Use Of Postmastectomy Radiation Therapy Research Articles

Identifying factors impacting the efficacy of postmastectomy radiotherapy in patients with early-stage breast cancer and one to two positive lymph nodes.

In women with T1-2 breast cancer and one to two positive axillary lymph nodes (LN) at low risk for recurrence, postmastectomy radiation therapy (PMRT) may provide insufficient benefit to justify its toxicity. This study evaluated the interaction of factors associated with overall survival (OS) after PMRT in these patients. The National Cancer Database was queried for women with T1-2 breast cancer undergoing mastectomy with one to two positive LN identified on lymphadenectomy. Patients were grouped according to number of positive LN and then stratified by PMRT use. Differences in OS were evaluated. Multivariable modeling demonstrated an interaction effect of age on the efficacy of PMRT. In patients more than or equal to 60 years old, PMRT was associated with improved survival when adjusting for age and tumor grade in patients with 1 to 2 positive LN (risk ratio = 0.62, 95% confidence interval = 0.40-0.93, P = .018). In patients less than 60 years old, tumor size and grade, but not PMRT, were associated with improved OS. For women with T1-2 breast cancer and one to two positive LN, PMRT's association with OS is influenced by age, tumor grade, and number of positive LN. PMRT appears to be associated with improvements in OS in older patients, but not younger patients, regardless of tumor size or nodal status.

Direct-to-Implant, Prepectoral Breast Reconstruction: A Single-Surgeon Experience with 201 Consecutive Patients.

The resurgence of prepectoral breast reconstruction has brought strict patient inclusion and exclusion criteria by numerous authors. This article provides an overview of a single surgeon's experience with 201 patients, 313 breasts using immediate, direct-to-implant prepectoral breast reconstruction. The article compares surgical outcomes of different patient cohorts to elucidate risk factors that may predispose patients toward developing complications. A retrospective chart review was performed, identifying all patients who underwent prepectoral, direct-to-implant breast reconstruction from June of 2016 to June of 2018. A total of 201 patients representing 313 breasts were included. A midlateral incision was used in 157 breasts (50.2 percent), followed by a skin-reducing, Wise-pattern in 90 breasts (28.8 percent). Acellular dermal matrix was used in 243 breasts (77.6 percent), free nipple grafts were used in 39 breasts (12.5 percent), and postmastectomy radiation therapy was used in 58 breasts (18.5 percent). Complications requiring operative intervention occurred in 24 breasts (7.7 percent), and minor complications occurred in 23 breasts (7.3 percent). There were no significant differences in complication rates for (1) acellular dermal matrix use versus non-acellular dermal matrix use, (2) Wise-pattern versus other incision, or (3) postmastectomy radiotherapy (p > 0.05). This represents the largest single-surgeon, direct-to-implant prepectoral cohort in the literature. Surgical complications did not differ with acellular dermal matrix use, incision selection, and the use of postmastectomy radiation therapy. There may be an association between acellular dermal matrix use and major complications and radiotherapy with minor complications. Therapeutic, III.

Real-world impact of postmastectomy radiotherapy in T1-2 breast cancer with one to three positive lymph nodes.

BackgroundThe utility of postmastectomy radiotherapy (PMRT) in breast cancer patients with T1–2 (tumor size ≤5 cm) and N1 (one to three lymph nodes involved) disease remains controversial. The aim of this population-based study was to investigate the effectiveness of PMRT in this patient subset in the current clinical practice.MethodsWe included T1–2N1 breast cancer patients treated with mastectomy from 2004 to 2012 using the data form the Surveillance, Epidemiology, and End Results program. The association of PMRT administration with breast cancer-specific survival was determined using multivariable Cox analysis.ResultsWe identified 10,248 patients of this study, including 3,725 (36.3%) received PMRT and 6,523 (63.7%) patients did not receive PMRT. Use of PMRT showed increase from 2008 onward; the percentage of patients receiving PMRT was 30.6% in 2004 and was 47.1% in 2012 (P<0.001). Patients diagnosis after 2008, aged <50 years, high tumor grade, T2 stage, and ≥2 positive lymph nodes were independently related to PMRT receipt. Multivariate analysis indicated that PMRT was not related to better breast cancer–specific survival compared to those without PMRT both before (P=0.186) and after propensity score matching (P=0.137).ConclusionsIn breast cancer with T1–2N1 disease, PMRT does not appear to improve survival in the era of modern systemic therapy.

Abstract P6-13-07: Cost-effective care for newly diagnosed breast cancer patients: Think globally, act locally

Abstract Conscientious use of scarce health economic resources allows for social distributive justice by avoiding over-treatment of patients to allow for appropriate treatment for a broader patient population. Lower socioeconomic status patients with breast cancer have a worse outcome compared to higher socioeconomic status patients in the United States. In part, this is due to poor access to medical care and a failure of logistical care. We implemented a community based breast cancer multidisciplinary program with weekly meetings to discuss patients, coordinate care, and provide cost-effective care to a medically under-served and vulnerable patient population. Breast surgery and medical oncology providers saw patients together in a co-located space and expedited timely initiation of neoadjuvant and adjuvant chemotherapy / hormone therapy for appropriate patients. The conjoint clinic allowed for rapid temporal integration of care in our safety net hospital / community. A single breast cancer navigator provided rapid identification of patients, coordination through clinics, and assistance with social work and other needs. Weekly 30 minute discussion sessions reviewing all new and relevant follow up patient issues were implemented in lieu of a breast cancer tumor board for efficiency. The relevant published clinical literature was reviewed on an ongoing basis. Cost-effective care was obtained by implementing: 1) avoidance of post lumpectomy radiation for selected patients based on PRIME2 trial results, 2) judicious use of post-mastectomy radiation based on a careful re-analysis of the data, 3) avoidance of adjuvant/neoadjuvant Perjeta in HER2+ patients based on a lack of overall survival, 4) adoption of 6 month schedule of adjuvant Herceptin, 5) avoidance of excessive imaging by following NCCN guidelines and clinical judgment, 6) limiting dose dense chemotherapy to appropriate patients (ER- high risk node negative or node positive), and 7) No Nernyx. Using a cost-effectiveness analysis methodology, we are reviewing costs, effectiveness of interventions, and risks with outcomes measured from side effects, complications, recurrence, and mortality. The improvement in temporal parameters and economic endpoints are being currently monitored retrospectively and prospectively and will be presented. Citation Format: Annie Tang, Shannon Ugarte, Rohan John, Amal Khoury, Kevin Knopf. Cost-effective care for newly diagnosed breast cancer patients: Think globally, act locally [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P6-13-07.

Breast journal 2020 special issue: Post-mastectomy radiation: Tracking changes in the standard of care over 25years.

This is an invited review article, tracking the changes in the indications and use of post-mastectomy radiation over the last 25years. While radiation after mastectomy has been in use for decades, several key prospective randomized trials published in recent years have changed and strengthened role of this modality. This manuscript will track the milestones over the last three decades.

Use of Postmastectomy Radiation in Patients Treated for Invasive Breast Cancer with Mastectomy and Immediate Reconstruction

Immediate reconstruction after mastectomy helps women manage the psychological impact of deforming surgery. Postmastectomy radiation therapy (PMRT) can negatively impact the aesthetic result after breast reconstruction. We performed this study to achieve a better understanding of how PMRT is used after reconstruction in our institution. We conducted a retrospective review of a prospectively maintained database of all women who underwent mastectomy for invasive breast cancer followed by immediate reconstruction from 2006 to 2017. Patients were divided into two groups depending on whether PMRT was included in their treatment, and we compared clinical and pathologic characteristics to determine which factors were likely to lead to PMRT. A total of 315 women treated with mastectomy and immediate reconstruction were identified. A total of 96 were treated with PMRT; 219 had mastectomy and immediate reconstruction without radiotherapy. Tumor characteristics, tumor stage, demographics, and comorbidities did not predict the use of PMRT. Neoadjuvant chemotherapy (NAC) was the most powerful predictor for using PMRT. In 47 of 81 (58%) patients treated with NAC, PMRT was used. Whereas 49 of 234 (21%) patients who did not receive NAC were treated with PMRT (P = 0.0001, risk ratio 2.77, 95 per cent confidence interval 2.03-3.77). In our institution, patients treated with NAC followed by mastectomy and immediate reconstruction are significantly more likely to receive PMRT. The increased use of PMRT after NAC should be factored into the preoperative discussion with patients choosing mastectomy and immediate reconstruction.

224P - A critical appraisal of quality indicators of breast cancer treatment in Belgium

BackgroundA task force was created by the Belgian Society of Medical Oncology (BSMO) to monitor the quality of treatment of breast cancer in Belgium. In collaboration with the Belgian Cancer Registry an analysis of the data was performed in search of reliable quality indicators. Finding actionable differences can lead to better treatment of our patients. MethodsData of 48,872 patients diagnosed with invasive breast cancer between 2010 and 2014 were analysed. To enable risk stratification according to their surrogate subtype, pathology reports of year 2014 were manually checked (9,855 patients). We identified patients < 70 Y (years) and > 75 Y receiving adjuvant radiotherapy after mastectomy and the different systemic treatments in each surrogate subtype. We also calculated the total length of endocrine treatment and the percentage of chemotherapy given in first line ER+ metastatic patients. ResultsIn cStage I-III, post-mastectomy radiotherapy was administered in 70.7% of the patients <70 Y and in 46.5% of patients > 75 Y, with an important intercenter variability. 81.7% of the cStage I-III patients <70 Y received at least 4.5 years of adjuvant endocrine therapy, with a slight decrease each year. In the 2014 cohort we identified 54.4% luminal A-like, 14.9% luminal B-like HER2-, 12.4% luminal B-like HER2+, 4.6% non luminal HER2+, 8.6% triple negative and 5.1% unknown. As a negative indicator, 44.6% of the HER2+ pT1aN0 patients <70 Y received adjuvant trastuzumab, compared to 22.2% of the patients > 70 Y. As first treatment for cStage IV HR+/HER2- patients, we identified endocrine therapy in 53.9% and chemotherapy in 17.3%. ConclusionsSubstantial treatment differences were observed among centers. Overtreatment is an important negative quality aspect of breast cancer management. A frequent use of postmastectomy radiotherapy was observed. The use of trastuzumab was inappropriate in pT1aN0 patients. Chemotherapy was used too often in first line hormone receptor positive metastatic patients. Legal entity responsible for the studyBelgian Cancer Registry. FundingHas not received any funding. DisclosureAll authors have declared no conflicts of interest.

Effect of postmastectomy radiotherapy on triple-negative breast cancer with T1-2 and 1-3 positive axillary lymph nodes: a population-based study using the SEER 18 database.

There is consensus on the routine use of postmastectomy radiotherapy (PMRT) in patients with four or more positive axillary lymph nodes. However, the benefits of PMRT in patients with T1-2 and 1-3 involved lymph nodes still remain controversial. Data from the Surveillance, Epidemiology, and End Results Program (SEER) of the United States between 2010 and 2012 were used to analyze the outcomes of 675 triple-negative breast cancer (TNBC) patients with T1-2 and 1-3 lymph nodes involved. Those patients were subdivided into radiotherapy (RT) (312) and no-RT groups (363). After a median follow-up time of 37 months, Kaplan-Meier analysis showed that PMRT significantly improved overall survival (OS) but not breast cancer-specific survival (BCSS) in the total cohort of 675 patients (P=0.033 and P=0.063). And it was demonstrated that PMRT were independently associated with increased OS according to univariate and multivariate analyses. However, no significant differences in BCSS or OS were observed between the groups stratified by the number of positive lymph nodes. In conclusion, PMRT significantly improved OS for TNBC patients with T1-2 and 1-3 lymph nodes involved. Additional prospective studies are needed to provide a stronger evidence base for choosing patients for PMRT.

Radiotherapy after skin-sparing mastectomy with immediate breast reconstruction in intermediate-risk breast cancer : Indication and technical considerations.

Skin-sparing (SSME) and nipple-sparing mastectomy (NSME) were developed to improve the cosmetic results for breast cancer (BC) patients, both allowing for immediate breast reconstruction. Recommendations for post-mastectomy radiotherapy (PMRT) are primarily derived from trials where patients were treated by standard mastectomies. Due to their more conservative character, SSME and especially NSME potentially leave more glandular tissue at risk for subclinical disease. Rates and sites of locoregional failures following SSME and NSME plus/minus reconstruction were analyzed regarding tumor stage and biological risk factors. In particular, the role of PMRT in "intermediate"-risk and early stage high-risk breast cancer patients was revisited. Implications on targeting and dose delivery of PMRT were critically reviewed. The value of PMRT in stageIII BC remains undisputed. For node-negative BC patients, the majority of reports classify clinical and biological features such as tumor size, close surgical margins, premenopausal status, multicentricity, lymphangiosis, triple-negativity, HER2-overexpression, and poor tumor grading as associated with higher rates of locoregional relapse, thus, building an "intermediate" risk group. Surveys revealed that the majority of radiation oncologists use risk-adaptive models also considering the number of coinciding factors for the estimation of recurrence probability following SSME and NSME. Constellations with a10-year locoregional recurrence risk of >10% are usually triggering the indication for PMRT. There was no common belief that the amount of residual tissue, e.g., tissue thickness over flaps, serves as additional decision aid. Modern treatment planning can ensure optimal dose distribution for PMRT in almost all patients with SSME. There are no reliable data supporting areduction of the treatment volume from the CTV chest wall, e.g., to the nipple-areola complex, to the dorsal aspect behind the implant volume, the pectoralis muscle, nor the regional interpectoral, axillary, or complete regional lymph nodes only. The omission of askin bolus in intermediate-risk BC does not compromise oncological safety. For intermediate-risk as well as early stage high-risk BC patients, the DEGRO Breast Cancer Expert Panel recommends the use of PMRT following SSME and NSME when a10-year locoregional recurrence risk is likely to be greater than 10%, as estimated by clinical and biological risk factors. Subvolume-only radiation is discouraged outside of trials. The impact of adequate systemic treatment and the value of radiotherapy on optimal locoregional tumor control, with the goal of less than 5% LRR at 10-years follow-up, has to be verified in prospective trials.

Individualized Prediction of Survival Benefit from Postmastectomy Radiotherapy for Patients with Breast Cancer with One to Three Positive Axillary Lymph Nodes.

There still exist some arguments regarding the use of postmastectomy radiotherapy (PMRT) for patients with breast cancer carrying one to three positive axillary lymph nodes considering the heterogeneity of this cohort. Here, we developed a prognostic nomogram to estimate the probability of long-term outcome in patients receiving or not receiving PMRT in order to assist in making individually locoregional treatment decisions for this particular cohort. Altogether, 20,336 women, aged 18 to 80 years, diagnosed with breast cancer, and carrying one to three positive nodes were identified in the Surveillance, Epidemiology, and End Results (SEER) database. We applied multivariant Cox hazard model to determine the impact of covariates on disease-specific survival (DSS) and overall survival (OS). Then, the nomogram was built accordingly. Internal and external validations were performed to examine the accuracy of nomograms. Age of diagnosis, tumor grade, size, estrogen and progesterone receptor status, and number of positive nodes were independent factors of DSS and OS in the multivariate analysis. Incorporating these factors into the constructed nomogram showed high accuracy when predicting 5- and 10-year survival, with internally and externally bootstrap-corrected concordance indexes in the range of 0.6 to 0.8. Besides the number of involved nodes, extra variables existed as predictors of survival outcomes in this cohort; therefore, the recommendation of PMRT or no PMRT requires comprehensive consideration. This clinically validated nomogram provided a useful tool that could aid decision making by estimating DSS and OS benefits from PMRT, useful in predicting 5- and 10-year DSS and OS for patients with one to three positive nodes after mastectomy. This study evaluated population-based data to identify prognostic factors associated with patients with breast cancer with one to three lymph nodes and help clinicians to weigh the benefit of postmastectomy radiotherapy (PMRT). Surveillance, Epidemiology, and End Results (SEER) data were used to develop a prognostic nomogram to predict the likelihood of long-term survival with and without PMRT in order to optimize the individual locoregional control strategy for this particular cohort. This clinically validated nomogram provides a useful tool to predict 5- and 10-year disease-specific survival and overall survival for patients with one to three positive nodes and can aid tailored clinical decision making by estimating predicted benefit from PMRT.

Postmastectomy radiation therapy in women with T1–T2 tumors and 1 to 3 positive lymph nodes: analysis of the breast international group 02-98 trial

In case of patients affected by breast cancer with more than 4 positive lymph nodes (LNs), postmastectomy radiation therapy (PMRT) has been widely adopted to reduce local relapse (1,2). Some controversies are still present regarding the use of PMRT for patients with 1–3 positive LNs.

Instrumental variable approach for estimating a causal hazard ratio: application to the effect of postmastectomy radiotherapy on breast cancer patients.

The use of postmastectomy radiotherapy (PMRT) on women with AJCC (American Joint Committee on Cancer) pT1-2pN1 breast cancer is controversial in practice. Huo et al. (2015) found that PMRT was associated with longer survival among a high-risk subgroup of AJCC pT1-2pN1 patients using a Cox model on data from the National Cancer Database. To address unmeasured confounding in this observational study, we consider the variation among facilities in the use of PMRT as an instrumental variable (IV). Recently, there has been widespread use of the two-stage residual inclusion (2SRI) method offered by Terza et al. (2008) for nonlinear models, and 2SRI has been the method of choice for analyzing proportional hazards model using IV in clinical studies. However, the causal parameter using 2SRI is only identified under a homogeneity assumption that goes beyond the standard assumptions of IV, and Wan et al. (2015) demonstrated that under standard IV assumptions, 2SRI could fail to consistently estimate the causal hazard ratio for compliers. In this paper, following Yu et al. (2015), we apply a model-based IV approach (Imbens and Rubin, 1997; Hirano et al., 2000) which allows consistent estimation of the causal hazard ratio for survival outcomes with a proportional hazards model specification under standard IV assumptions while flexibly incorporating the restrictions imposed by IV assumptions. Simulation studies show that when there is unmeasured confounding, both 2SRI and the standard Cox regression could provide biased estimates of the causal hazard ratio among compliers, while this model-based IV approach provides consistent estimates. We apply this IV method to the breast cancer study and our IV analysis did not find strong evidence to support the benefit of PMRT on survival among the targeted patients. In addition, we develop sensitivity analysis approaches to assess the sensitivity of causal conclusions to violations of the exclusion restrictions assumption for IV.

Postmastectomy radiation therapy for triple negative, node-negative breast cancer

PurposeThe use of post-mastectomy radiation therapy (PMRT) for patients with node-negative, triple negative breast cancer (TNBC) is controversial. This study of a large, contemporary US database described national practice patterns and addressed the impact of PMRT on survival for patients with node-negative TNBC. MethodsThe National Cancer Data Base was queried (2004–2014) for women with non-metastatic TNBC with pT1-4N0M0 disease undergoing mastectomy. Use of PMRT was assessed. Multivariable logistic regression ascertained factors associated with PMRT use. The Kaplan–Meier analysis evaluated overall survival (OS) between patients managed with either PMRT or observation following mastectomy when stratifying by pT stage. Cox proportional hazards modeling determined variables associated with OS. ResultsA total of 14,464 patients met the selection criteria; of these, 1,569 (10.8%) received PMRT, whereas 12,895 (89.2%) did not receive PMRT. Use of PMRT varied significantly with pT stage, with only 5.7% of T1 patients undergoing PMRT, while 51.6% of patients with T3 disease underwent PMRT. Use of PMRT was associated with superior OS for patients with pT3 disease but not for patients with other T stages. Greater age was associated with decreased likelihood of PMRT use, while increased T stage and positive surgical margins were associated with use of PMRT. On multivariate analysis, increased age, T stage, and positive surgical margins were associated with worse OS. ConclusionsIn the largest study to date evaluating the use of PMRT in patients with node-negative TNBC, the use of PMRT was low in patients with T1 and T2 disease. Additionally, while an OS benefit was observed with the use of PMRT in patients with T3 disease, there was no benefit with the use of PMRT in other T stage groups. Further prospective studies are recommended to further elucidate the benefit on PMRT in patients with node-negative TNBC.

Indications for and efficacy of postmastectomy radiotherapy for patients with a favorable response to neoadjuvant chemotherapy.

Prospective, randomized data regarding the use of postmastectomy radiotherapy (PMRT) in women who receive neoadjuvant chemotherapy (NAC) are lacking. The usefulness of PMRT in patients who respond well to NAC forms the basis of the ongoing National Surgical Adjuvant Breast and Bowel Project (NSABP) B51/Radiation Therapy Oncology Group (RTOG) 0413 clinical trial. Herein, the authors review the current literature examining the role of PMRT in women who receive NAC prior to surgery.

Clinical decision making in postmastectomy radiotherapy in node negative breast cancer.

For decades, postmastectomy radiotherapy (PMRT) has been recommended for node positive [N(+)] breast cancer patients; nevertheless, the beneficial effect of PMRT for treatment of node negative [N(−)] disease remains under discussion. Nowadays, the biology of breast cancer and the risk factors (RFs) for locoregional failure (LRF) must be included in the decision on whether or not to carry out PMRT. For these reasons, the present review aims to evaluate the rationale use of PMRT in N(−) patients and discuss which subgroups may further benefit from the treatment in present times where the decision must be personalised, according to the RFs of locoregional recurrence (LRR). To perform the analysis, we ponder that LRR of over 10% should be considered unacceptable due to the fact that LRRs generate great morbidity in patients. For this purpose, we consider that routine RT in these patients is not recommended, although there are subgroups of patients with high LRR, in which PMRT could be beneficial.

Post-mastectomy Radiation Therapy in Breast Cancer Patients with Nodal Micrometastases.

Recent data support the use of post-mastectomy radiation therapy (PMRT) in women with one to three positive lymph nodes; however, the benefit of PMRT in patients with micrometastatic nodal disease (N1mi) is unknown. We evaluated the survival impact of PMRT in patients with N1mi within the National Cancer Database. The pattern of care and survival benefit of PMRT was examined in women with pT1-2N1mi breast cancer who underwent mastectomy without neoadjuvant chemotherapy. Univariable and multivariable Cox proportional hazard models were employed for survival analysis, and subanalyses of high-risk patients and a propensity score-matched (PSM) cohort were completed. From 2004 to 2014, we identified 14,019 patients who fitted the study criteria. PMRT was delivered in 18.5% of patients and its use increased over the study period. Patients treated with PMRT were younger, had better performance status and larger primaries, were estrogen receptor (ER)-negative, had higher grade, lymphovascular invasion and positive surgical margins, and more often received systemic therapy. PMRT was significantly associated with overall survival (OS) in univariable analysis (hazard ratio [HR] 0.75 [0.64-0.89]), but was not significant in multivariable analysis (adjusted HR 1.01 [0.84-1.20]). There was no survival benefit to PMRT in ER-negative, high-grade, and/or young patients. There were 2 (0.9%) death events in the sentinel lymph node biopsy (SLNB) + PMRT group versus 21 (2.9%) in the SLNB-alone group (log-rank p = 0.053), and 8 (3.9%) death events in the axillary lymph node biopsy (ALNB) + PMRT group versus 27 (3.6%) in the axillary lymph node dissection-alone group (p = 0.82). There was no significant association between PMRT and OS within the PSM subgroup. In this largest reported retrospective study, no OS differences were associated with PMRT, which suggests that PMRT may not benefit every patient with microscopic nodal disease.

Treatment patterns for ductal carcinoma in situ with close or positive mastectomy margins

BackgroundMastectomy remains an effective treatment for ductal carcinoma in situ (DCIS) but whether further therapy is warranted for close or positive margins is controversial. We aim to characterize the treatment practices of DCIS throughout the United States in patients who undergo mastectomy with close or positive margins to better understand the use of postmastectomy radiation therapy (PMRT). Materials and methodsUsing the 2004-2013 National Cancer Database, we identified all female patients with a diagnosis of DCIS who underwent mastectomy. Distributional characteristics were summarized for overall and margin-stratified samples. Characteristic differences were assessed by region and receipt of radiation. Chi-square and independent sample t-tests were used to assess differences for categorical and continuous variables, respectively. ResultsIn 21,591 patients who met inclusion criteria, 470 patients with close/positive margins were identified. Sixteen percent of patients with close/positive margins received PMRT compared to 1.5% with negative margins (P < 0.01). There was no difference in PMRT and patient race, insurance status, treatment facility, or endocrine therapy. Patients with close/positive margins who received PMRT were more likely to be in an urban setting from the Midwest (24.6%) and Northeast (21.8%) compared to the West (11.0%) and South (10.7%) (P < 0.01). ConclusionsUse of PMRT for DCIS following mastectomy with close/positive margins differs across the country. Regional variations in treatment patterns reinforce a need to determine whether PMRT improves survival to establish treatment guidelines.

The Potential Impact of AMAROS on the Management of the Axilla in Patients with Clinical T1-2N0 Breast Cancer Undergoing Primary Total Mastectomy.

Recent trials have demonstrated that axillary observation or axillary radiation therapy (AxRT) is equivalent to axillary node dissection (ALND) for patients with one or two positive sentinel lymph nodes (SLNs). These strategies have been widely adopted for patients having breast conservation. This report demonstrates the potential impact of the AMAROS trial on axillary therapy in a retrospective cohort of mastectomy patients. Patients undergoing primary mastectomy for cT1-2N0 breast cancer who had one or two positive SLNs were identified from institutional databases (2005-2015). Locoregional management strategies were evaluated, and variables predictive of the use of postmastectomy radiation therapy (PMRT) were identified. Among 2594 mastectomies, 193 (7%) met the AMAROS eligibility criteria. The median patient age was 50years (range 22-83years). Locoregional treatment consisted of ALND + PMRT for 102 patients (53%), ALND alone for 66 patients (34%), PMRT alone for 11 patients (6%), and observation for 14 patients (7%). Overall, 59 ALND patients (35%) had additional positive nodes. In the multivariate analysis, age younger than 50years (odds ratio [OR] 3.55; 95% confidence interval [CI] 1.57-8.45), lymphovascular invasion (LVI) (OR 5.78; 95% CI 2.53-4.78), macrometastases (OR 3.99; 95% CI 1.54-10.97), and extracapsular extension (OR 11.66; 95% CI 2.55-88.34) were associated with receipt of PMRT. In this cohort of AMAROS-eligible patients, 168 (87%) underwent ALND, 102 (61%) of whom also received PMRT, suggesting that AxRT could have been used instead of ALND for a significant number of patients. Preoperative factors associated with the receipt of PMRT, such as young age and LVI, may be useful for defining a multidisciplinary decision-making framework for axillary management in this population.

Trends and Patterns of Utilization of Hypofractionated Postmastectomy Radiotherapy: A National Cancer Database Analysis

BackgroundThe acceptance of hypofractionated radiotherapy in treating breast cancer in the breast conservation therapy setting has stimulated interest in hypofractionated postmastectomy radiotherapy (PMRT). We assessed national trends and patterns of utilization of hypofractionated PMRT. Patients and MethodsWomen 18 years of age or older with breast cancer treated with mastectomy and PMRT to the chest wall with or without regional lymph nodes from 2004 to 2014 were identified from the National Cancer Database. A standard fractionation cohort was defined as patients receiving 180 to 200 cGy per fraction to a total dose of 4500 to 7000 cGy over 5 to 7 weeks, and a hypofractionation cohort was defined as those receiving 250 to 400 cGy per fraction to a total dose of 3000 to 6000 cGy over 2 to 5 weeks. Multivariable logistic regression was used to determine factors associated with hypofractionated PMRT use. ResultsWe identified 113,981 patients who met study criteria. Overall, hypofractionated PMRT use was low (1.1%) although utilization increased over time (P ≤ .001). Older age, greater comorbidity, further distance from treatment facility, treatment at academic facilities, less extensive disease, and recent treatment year were statistically significant predictors of hypofractionation use compared with standard fractionation. Conversely, breast reconstruction and receipt of chemotherapy were negative predictors. ConclusionBecause of the absence of high-level evidence to support its use, hypofractionated PMRT was uncommonly utilized in the United States from 2004 to 2014, although a small increase in use was noted over time. Findings from this study might be useful in designing future studies, and might serve as a baseline for evaluation of future changes in practice patterns.

Abstract ES1-2: Guidelines for postmastectomy radiotherapy

Abstract A joint panel of the American Society of Clinical Oncology (ASCO), American Society for Radiation Oncology (ASTRO), and Society of Surgical Oncology (SSO) convened in 2015 to develop an update of the prior ASCO guideline (J Clin Oncol 2001;19:1539-1569) concerning the use of postmastectomy radiation therapy (PMRT). This effort focused on common scenarios where there have been substantial controversy. Their conclusions and supporting evidence have been published (J Clin Oncol 2016;34:4431-4442). The Panel unanimously agreed that PMRT reduces the risks of local-regional failure (LRF), any recurrence, and breast cancer mortality for patients with T1-2 breast cancer with 1-3 positive axillary nodes. However, some subsets of these patients are likely to have such a low risk of LRF that the absolute benefit of PMRT is outweighed by its potential toxicities. The Panel however could not find sufficient evidence to recommend a specific formula or method of how to combine clinical, pathologic, and biologic data to calculate the risk of LRF. In addition, the acceptable ratio of benefit to toxicity varies among patients and physicians. Thus, the decision to recommend PMRT or not requires a great deal of clinical judgement. The Panel agreed clinicians making such recommendations for an individual patient should consider factors that may decrease the risk of LRF, attenuate the benefit of reduced breast cancer-specific mortality, and/or increase the risks of complications from PMRT. When clinicians and patients elect to omit axillary dissection after a positive sentinel node biopsy, the Panel recommended that these patients receive PMRT only if there is already sufficient information to justify its use without needing to know that additional axillary nodes are involved. Patients with axillary nodal involvement following neoadjuvant systemic therapy should receive PMRT. The role of PMRT in other patients with clinical Stage I or II breast cancer is uncertain. Finally, the Panel recommended that radiation therapy generally be given to both the internal mammary nodes and the supraclavicular-axillary apical nodes in addition to the chest wall or reconstructed breast when PMRT is used. However, there may be subgroups that will have limited, if any, benefits from treating both these nodal areas compared to treating only one of them or, perhaps, treating only the chest wall or reconstructed breast. There is insufficient evidence at this time to define such subgroups in detail. This lecture will address selected elements of the data leading to the Panel's decisions. Citation Format: Recht A. Guidelines for postmastectomy radiotherapy [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr ES1-2.