Benefit of Adjuvant Brachytherapy Versus External Beam Radiation for Early Breast Cancer: Impact of Patient Stratification on Breast Preservation

Purpose Brachytherapy after lumpectomy is an increasingly popular breast cancer treatment, but data concerning its effectiveness are conflicting. Recently proposed "suitability" criteria guiding patient selection for brachytherapy have never been empirically validated. Methods Using the Surveillance, Epidemiology, and End Results–Medicare linked database, we compared women aged 66 years or older with invasive breast cancer (n=28,718) or ductal carcinoma in situ (n=7229) diagnosed from 2002 to 2007, treated with lumpectomy alone, brachytherapy, or external beam radiation therapy (EBRT). The likelihood of breast preservation, measured by subsequent mastectomy risk, was compared by use of multivariate proportional hazards, further stratified by American Society for Radiation Oncology (ASTRO) brachytherapy suitability groups. We compared 1-year postoperative complications using the χ 2 test and 5-year local toxicities using the log-rank test. Results For patients with invasive cancer, the 5-year subsequent mastectomy risk was 4.7% after lumpectomy alone (95% confidence interval [CI], 4.1%-5.4%), 2.8% after brachytherapy (95% CI, 1.8%-4.3%), and 1.3% after EBRT (95% CI, 1.1%-1.5%) ( P P =.84 for interaction), although ASTRO "suitable" patients did show a low absolute subsequent mastectomy risk, with a minimal absolute difference in risk after brachytherapy (1.6%; 95% CI, 0.7%-3.5%) versus EBRT (0.8%; 95% CI, 0.6%-1.1%). For patients with ductal carcinoma in situ, EBRT maintained a reduced risk of subsequent mastectomy (HR, 0.40; 95% CI, 0.28-0.55; P P P P Conclusions In this study era, brachytherapy showed lesser breast preservation benefit compared with EBRT. Suitability criteria predicted differential absolute, but not relative, benefit in patients with invasive cancer.