Once-Weekly Hypofractionated Whole-Breast Radiotherapy After Breast-Conserving Surgery in Older Patients: A Potential Alternative Treatment Schedule to Daily 3-Week Hypofractionation.

Background: The purpose of this study was to retrospectively report clinical outcomes on a consecutive series of older early breast cancer patients treated with once-weekly adjuvant whole-breast radiation therapy (WBRT) after breast-conserving surgery (BCS).

Methods: A total of 291 patients (298 breasts) were treated with WBRT between 2007 and 2013. Patients were given 6 to 6.5 Gy in 5 weekly fractions (total dose, 32.5-30 Gy) over 5 weeks. Clinical end points were local control (LC), disease-free (DFS), cancer-specific (CSS), and overall survival (OS), and acute and late toxicity and cosmesis. Prognostic clinical variables were assessed with respect to DFS.

Results: Median follow-up was 46.5 months (range, 12-84 months). The 3- and 5-year LC rates were 99.5% (95% confidence interval [CI], 96.4-99.9) and 98% (95% CI, 91.1-99.6). The 3- and 5-year CSS and OS were 97.7% (95% CI, 94.5-99.1), 95.3% (95% CI, 90.5-97.7), 94.4% (95% CI, 90.4-96.7), and 83.6% (95% CI, 76.1-88.9), respectively. Maximum detected acute skin toxicity was Grade (G) 0 in 71.8% of patients, G1 in 22.6%, G2 in 4.8%, G3 in 1%, and G4 in 0.3%. Treatment interruption occurred in 2 patients because of severe skin reactions. Late skin toxicity consisted of G1 fibrosis in 31.5% of patients, G2 in 4.2%, and G3 in 3.5%. Grade 1 edema was observed in 7% of patients, G2 in 4.2%, and G3 in 1.4%. G1 telangiectasia occurred in 1.8% and G3 in 0.7%. G1 hyperpigmentation was found in 4.6% of patients, G2 in 2.4%, and G1 atrophy was detected in 2.1%. Pain was observed as G1 in 13%, G2 in 1.8%, and G3 in 0.4%. Cosmetic results were good to excellent in 86.4% and fair to poor in 13.6%.

Conclusions: Once-weekly hypofractionated WBRT (30-32-5 Gy in 5 fractions), delivered with standard tangential fields with the patient in the supine position seems feasible and effective for a selected population of primarily old breast cancer patients with predominantly low-risk features. This schedule might allow fragile patients to receive adjuvant WBRT after BCS, increasing radiotherapy accessibility and utilization.