Prophylactic supraclavicular radiotherapy after surgery in high-risk N1 breast cancer

Objectives: To evaluate the role of prophylactic supraclavicular radiotherapy (RT) by comparing the clinical outcomes of locoregional recurrence (LRR) in high-risk N1 breast cancer. Methods: We performed a retrospective comparison study of 250 high-risk N1 breast cancer patients treated at two institutions. Patients were considered to be high-risk when they had more than two of the following risk factors: lymphovascular invasion, extracapsular extension, metastasis to more than two axillary lymph nodes (ALNs), or level II or higher ALN metastasis. We compared two groups treated with different adjuvant RT fields for the purpose of prophylactic supraclavicular RT (SCRT). Results: Among the 250 patients, 97 patients received SCRT while 153 did not. During follow-up, 32 patients (7 in the SCRT and 25 in the no-SCRT group) had recurrence, and LRR developed in 19 patients, 18 of whom had not received SCRT. In multivariate analysis, SCRT [hazard ratio (HR) 0.072; p = 0.011] and chemotherapy regimen (cyclophosphamide, Adriamycin, and taxane; TAC) were the significant prognostic factors in LRR-free survival (HR 0.385; p = 0.046), and chemotherapy regimen also showed significance for distant metastasis-free survival (HR 0.399; p = 0.037). Conclusions: Use of prophylactic SCRT may reduce the risk of LRR in patients with high-risk N1 breast cancer.