External Beam Accelerated Partial-Breast Irradiation Using 32 Gy in 8 Twice-Daily Fractions: 5-Year Results of a Prospective Study

Overall outcomes were excellent, particularly for patients with estrogen receptor-positive disease. Patients in this study with triple-negative breast cancer had a significantly higher IBTR rate than patients with other receptor phenotypes when treated with 3D-APBI. Larger, prospective 3D-APBI clinical trials should continue to evaluate the effect of hormone receptor phenotype on IBTR rates.