Locoregional and Distant Outcomes in Women With cT1-3N1 Breast Cancer Treated With Neoadjuvant Chemotherapy With or Without Adjuvant Radiotherapy.

ABSTRACT

BACKGROUND: We evaluated the impact of postmastectomy radiotherapy (PMRT) or supraclavicular radiation therapy (SCV RT) in women with cT1-3N1 breast cancer (BC) who became node negative (ypN0) after neoadjuvant chemotherapy (NAC). PATIENTS AND METHODS: We retrospectively reviewed 485 women treated with NAC for BC between 2005 and 2019. Radiation treatment fields were reviewed in detail. Pathologic complete response (pCR) was defined as ypT0/Tis ypN0. Patients who had residual nodal disease were defined as ypN+. Those who achieved complete response in the lymph nodes but not in the breast were defined as ypT+ypN0. RESULTS: After excluding patients with cT4 and cN0 disease at diagnosis, a total of 185 patients with cT1-3N1 BC were included. Patients were more likely to receive PMRT if they had ypN+ disease (P < .001) and/or lymphovascular invasion (P = .03). Patients who underwent lumpectomy were more likely to receive SCV RT if they did not achieve pCR (P = .04) and/or if they had ypN+ disease (P = .01). The 5-year rates of locoregional recurrence (LRR) were 15% for all patients, 14% for patients who attained ypT+ypN0, and 5% for patients who achieved pCR. Of ypT+ypN0 patients (n = 98), 53 received PMRT or SCV RT and 45 did not. For these patients, there were no differences in LRR based on whether a patient did or did not receive PMRT or SCV RT (P = .23). CONCLUSION: Recommendations for or against PMRT or SCV RT after NAC vary based on final pathologic response. We await the results of ongoing randomized clinical trials to help guide clinical decision making in this context.