Ten-Year Survival after Postmastectomy Chest-Wall Irradiation in Breast Cancer

BACKGROUND: The role of postmastectomy chest-wall irradiation in patients with breast cancer classified as pN1 (with involvement of one to three axillary nodes) or pN0 (pathologically node negative) with additional risk factors is uncertain. METHODS: In this international, phase 3, randomized trial, we evaluated the omission of chest-wall irradiation in women with "intermediate-risk" breast cancer - defined as cancer that was stage pT1N1, pT2N1, or pT3N0 or stage pT2N0 with a histologic grade of 3, lymphovascular invasion, or both (tumor size: T1, ≤2 cm; T2, >2 cm to 5 cm; or T3, >5 cm) - that was treated with mastectomy, an axillary procedure, and systemic therapy. Patients were assigned to undergo chest-wall irradiation (40 to 50 Gy; the irradiation group) or not to undergo chest-wall irradiation (the no-irradiation group). The primary end point was overall survival, with 10 years of follow-up. Chest-wall recurrence, regional recurrence, disease-free survival, distant metastasis-free survival, causes of death, and radiation-related adverse events were also assessed. RESULTS: The intention-to-treat population included 808 patients in the irradiation group and 799 in the no-irradiation group. The median follow up was 9.6 years. Overall survival was 81.4% with chest-wall irradiation and 81.9% with no chest-wall irradiation according to 10-year Kaplan-Meier estimates (hazard ratio for death, 1.04; 95% confidence interval [CI], 0.82 to 1.30; P = 0.80). A total of 29 patients had a chest-wall recurrence - 9 (1.1%) in the irradiation group and 20 (2.5%) in the no-irradiation group (between-group difference, <2 percentage points; hazard ratio, 0.45; 95% CI, 0.20 to 0.99). Disease-free survival was 76.2% in the irradiation group and 75.5% in the no-irradiation group (hazard ratio for recurrence or death, 0.97; 95% CI, 0.79 to 1.18), and distant metastasis-free survival was 78.2% and 79.2%, respectively (hazard ratio for distant metastasis or death, 1.06; 95% CI, 0.86 to 1.31). CONCLUSIONS: In this trial, chest-wall irradiation did not result in higher overall survival than no chest-wall irradiation among patients with intermediate-risk, early breast cancer treated with mastectomy and contemporary adjuvant systemic therapy. (Funded by the Medical Research Council and others; SUPREMO ISRCTN Clinical Study Registry number, 61145589.).