Evidence-based indications for post-mastectomy radiation after neoadjuvant chemotherapy for stage II-III breast cancer.

Abstract

114 Background: There are no established guidelines to define the role of post-mastectomy radiation therapy after neoadjuvant chemotherapy. We sought to identify a cohort of women with stage II-III breast cancer in whom radiation may be omitted based on the risk of local-regional failure (LRF). Methods: Seven breast cancer physicians participating in the multi-campus University of California (UC) Athena Breast Health Network identified, reviewed and abstracted the available literature (from MEDLINE and Cochrane databases), formulated evidence tables (endpoints LRF, disease-free, and overall survival) and developed a risk assessment table of women undergoing mastectomy after neoadjuvant chemotherapy. We created 18 hypothetical clinical case scenarios, and using the American College of Radiology appropriateness criteria methodology, assigned appropriateness ratings for post-mastectomy radiation for each scenario based on our literature review. Results: 23 of 24 studies identified were retrospective from single institutions. Consensus (80% agreement in a category) in the appropriateness rating was achieved for 78% of the clinical scenarios. Distinct LRF risk categories emerged. Patients who presented with clinical stage II (T1-2N0-1) ER(+) disease with age at diagnosis ≥35-40 years who had either a pathologic complete response (pCR) or 0-3 positive nodes without LVI or ECE were identified as having ≤10% risk of LRF without radiation. Limited data support pCR stage IIIA patients as being low risk. Conclusions: In the absence of randomized trial data, we identified existing data to guide the use of PMRT in the neoadjuvant chemotherapy setting. Using this data and the appropriateness ratings, we found a high concordance of treatment recommendations for PMRT in our clinical scenarios and were able to identify a cohort of women with a low risk of LRF without radiation. These women will form the basis for future clinical studies in the UC Athena Breast Health Network.