Importance Evolving data on the effectiveness of post-mastectomy radiation therapy (PMRT) have led to changes in NCCN recommendations counseling providers to “strongly consider” PMRT for breast cancer patients with tumors ≤5cm and 1-3 positive nodes; however anticipated PMRT may lead to delay or omission of reconstruction which can have cosmetic quality of life and complication implications for patients. reconstruction increased in other groups. Design A retrospective population-based cohort study Setting Surveillance Epidemiology and End Results (SEER) data from 2000 – 2011. Participants Women with stage I-III breast cancer undergoing mastectomy were identified. Our analytic sample (n=62 442 was divided into cohorts based on current NCCN radiation recommendations: “Radiation Recommended” (tumors >5 cm or ≥4 positive lymph nodes) “Strongly Consider Radiation” (tumor ≤5cm 1 positive nodes) and “Radiation Not Recommended” (tumors ≤5cm no positive nodes). Main Outcome Measure(s) We used joinpoint regression analysis to evaluate temporal trends in our outcomes of interest: receipt of PMRT and receipt of breast reconstruction. Results Rates of PMRT were unchanged in the “Radiation Recommended” and “Radiation Not Recommended” cohorts over the study period. In contrast receipt of PMRT for the “Strongly Consider Radiation” cohort was unchanged until 2007 then significantly increased (APC 9.0% p=0.013). Breast reconstruction increased across all cohorts. Despite increasing receipt of PMRT the “Strongly Consider Radiation” cohort maintained a consistent increase in reconstruction (APC 7.5%) throughout the study period. This is Alfuzosin HCl similar to the increase in reconstruction observed for the “Radiation Recommended” (10.7%) and “Radiation Not Recommended (8.4%) cohorts. Conclusions and Relevance NCCN guideline changes have increased PMRT receipt for patients with tumors ≤5cm and 1-3 positive nodes without an associated decrease in receipt of reconstruction. This may represent increasing provider comfort with the prospect of irradiating a new breast reconstruction and may have significant cosmetic and quality of life implications for patients. Introduction In the past decade indications for the use of post-mastectomy GP1BA radiation therapy (PMRT) have expanded. Prior to the year 2000 several trials demonstrated decreased loco-regional recurrence as well as improved survival in breast cancer patients with tumors >5 cm positive lymph nodes and/or Alfuzosin HCl invasion of skin or pectoral fascia who received PMRT plus mastectomy and axillary clearance versus mastectomy and axillary clearance alone 1 establishing a standard of care for who should be considered for PMRT. In Alfuzosin HCl subgroup analyses of these initial studies the observed benefits of PMRT persisted Alfuzosin HCl in patients with 1-3 positive lymph nodes with a decrease in loco-regional recurrence from 27% to 4% (p<0.001) and a corresponding increase in overall survival from 48% to 57% (p=0.03)4. Further data supporting the benefit of PMRT for patients with 1-3 positive lymph nodes was presented by the Early Breast Cancer Trialists’ Collaborative Group (EBCTCG) in 2005. Although the magnitude of the absolute reduction in loco-regional recurrence was lower in this meta-analysis (11.6%) than in the RCTs similar trends were observed with a 4.4% improvement in 15-year breast cancer survival for patients who underwent mastectomy axillary clearance and PMRT compared to surgery alone.5 Based on these findings the National Comprehensive Cancer Network (NCCN) expanded its treatment guidelines to “strongly consider” PMRT for patients with tumors ≤5 cm and 1-3 positive lymph nodes.6 However the role of PMRT for patients with 1-3 positive lymph nodes remains controversial due to the relatively high rate of local recurrence observed in these trials combined with advances in systemic and targeted therapies since completion of the trial. Concurrently there has been a rapid expansion in the use of immediate breast reconstruction over the past two decades.7 8 Breast reconstruction appears to significantly Alfuzosin HCl improve quality of life 9 10 and immediate reconstruction reduces the adverse psychosocial effects associated with mastectomy 11 can streamline treatment by reducing the number of necessary surgeries and is favored by women compared to delayed reconstruction.12 However in the setting of anticipated PMRT reconstruction decision-making becomes more complicated: Alfuzosin HCl prior studies suggest that both radiation oncologists and plastic surgeons have reservations about the use of immediate reconstruction in the setting of PMRT. The majority of radiation oncologists believe that immediate.