['Radiotherapy (RT) reduces local recurrence after breast-conserving surgery (BCS) for breast cancer, but under-utilization of RT has been reported. Accelerated partial-breast irradiation (PBI) improves RT accessibility, but it is uncertain if this has improved RT utilization.', 'The Surveillance, Epidemiology and End Results registry was used to identify women who underwent BCS for stage 0 or 1 breast cancer from 2000 to 2009. Temporal trends in RT utilization and RT modality were determined. Chi-square analysis and multivariate logistic regression identified predictors of RT utilization and modality.', 'Of 180,219 study patients, 131,343 (73 %) received RT; 123,703 (94 %) of RT recipients received whole-breast irradiation (WBI) and 6,251 (5 %) received PBI. PBI rates increased dramatically during the study period (0.32 % in 2000 vs. 6.5 % in 2009), but overall RT utilization remained relatively stable because of a decline in WBI (69.8 % in 2000 vs. 62.4 % in 2009). RT utilization was unchanged in rural counties, and declined for women <40 and ≥70 years of age, and for Native American, Asian and Hispanic patients. White and Black women used PBI most frequently (4 % each) and were the only race groups with improved RT utilization over time. Predictors of RT usage included age, race, marital status, tumor size, grade, hormone receptor status, lymph node evaluation, geographic region, metropolitan status, education, and employment status.'] Has increased use of partial-breast irradiation improved radiotherapy utilization for early-stage breast cancer?