84 Background: APBIb is a novel alternative to whole breast irradiation (WBI). The American Society for Radiation Oncology Guidelines (ASTRO-G) established appropriateness for APBIb use off protocol. Methods: 138,815 bca patients from the Surveillance, Epidemiology, and End Results database underwent WBI or APBIb after lumpectomy from 2000 to 2007. Patients were classified as suitable, cautionary, or unsuitable for APBIb according to ASTRO-G. Logistic regression was applied to study APBIb use overall and within each guideline category. Results: Overall, 2.6% received APBIb and use varied by ASTRO-G: 5% in suitable, 3.4% in cautionary, and 1.6% in unsuitable patients (p<0.0001). APBIb use increased with time (2000: 0.3%, 2007: 7%) and varied widely with region (0% Alaska; 7% Atlanta, Georgia). Independent predictors of APBIb among suitable patients included white (OR 2.0, p<0.001) race, region (OR 2.6-8.6, p<0.0001), later year (2006-7 v 2000-2 OR 20.3, p<0.0001), and lower grade (OR 1.3, p=0.01). Among cautionary patients, white race (OR 1.8, p<0.001), non-Hispanic ethnicity (OR 1.3, p<0.04), region (OR 3.1-10.2, p<0.0001), metropolitan location (OR 1.9, p=0.01), later year (2006-2007 OR 17.6, p<0.0001), and lower grade (OR 1.4, p<0.0001) predicted for APBIb. Among unsuitable patients, race (p<0.0001), region (OR 3.3-21.6, p<0.0001), later year (2006-7 OR 12.7, p<0.0001), estrogen receptor-positive status (OR 1.3, p=0.002), lower grade (OR 1.3, p<0.01), and negative lymph nodes (OR 2.0, p<0.0001) predicted for use. In several regions, odds of APBIb increased as appropriateness decreased (see Table). Conclusions: APBIb has been rapidly adopted in the US. Its use varied by race, ethnicity, and region, especially among patients who may not be suitable candidates for this technique. [Table: see text]
Five-year outcome of patients classified using the American Society for Radiation Oncology consensus statement guidelines for the application of accelerated partial breast irradiation
