RESUMO
PURPOSE: This study aimed to evaluate the outcome of patients who had received postmastectomy chest wall radiotherapy using a single electron beam, and to identify the relevant factors that influenced prognosis. METHODS: The medical records of patients with breast cancer treated with postmastectomy radiotherapy from January 2000 to December 2004 were retrospectively analyzed (n = 328). Two hundred seventy-one (82.6%) patients were staged as (tumor-nodes-metastasis [TNM]) T3-4, any N, M0; or T1-2, N2-3, M0, and 57 (17.4%) patients were staged as T1-2, N1, M0. All patients received chest wall radiation with a 6-10 MeV electron beam. In addition, 327 patients (99.7%) received supraclavicular node radiation, 67 (20.4%) axillary radiation, and 35 (10.7%) internal mammary chain (IMC) radiation. Chemotherapy with anthracycline and taxane was given to 323 patients (98.5%). Of patients with positive hormone receptor, 183 (82.8%) received hormone therapy and 8 patients with negative and 3 patients with unknown hormone receptor received hormone therapy. Locoregional recurrence (LRR), distant metastasis (DM), and overall survival (OS) were calculated using the Kaplan-Meier method, and the differences assessed by log-rank test. RESULTS: The median follow-up time was 78 months (range, 5-123 months) for patients who remained alive. The 5-year LRR, DM, disease-free survival and OS rates were 5.9%, 26.2%, 72.5%, and 83.1%, respectively. LRR occurred in 1 or more sites in 21 patients. The 5-year recurrence rates in the chest wall, supraclavicular node, axilla, and internal mammary chain were 1.9%, 2.3%, 2.9%, and 0%, respectively. In multivariate analysis, hormone therapy was the only independent favorable prognostic factor for LRR (P = .017). LRR was significantly associated with DM and OS. The 5-year DM rate was 82.9% and 22.7% (P < .0001) and the 5-year OS rate was 52.8% and 84.7% (P < .0001) for patients with or without LRR. The treatment-related toxicity was low, with the incidence of symptomatic pneumonitis being 0.3%. CONCLUSIONS: Breast cancer patients can be treated with postmastectomy single electron beam radiotherapy with excellent local control and low toxicity.