Evaluating Candidacy for Hypofractionated Radiation Therapy, Accelerated Partial Breast Irradiation, and Endocrine Therapy After Breast Conserving Surgery

Purpose/Objective(s): After breast conserving surgery, adjuvant radiation therapy represents the standard of care for most patients. However, multiple options exist beyond standard fractionated whole breast irradiation including hypofractionated whole breast irradiation (HFRT), accelerated partial breast irradiation (APBI), and endocrine therapy (ET) alone, which can limit treatment duration, and potentially reduce morbidity and cost. Limited data are available on the percentage of patients eligible for these alternatives; therefore, a Surveillance Epidemiology and End Results (SEER) analysis was performed to assess candidacy for these alternative options in women with early stage breast cancer. Materials and Methods: Women treated for breast cancer between the years of 2010 and 2012 were identified in the SEER database. Patients with unknown staging, metastatic disease, T3/T4 disease, and ≥N1 disease were excluded. Patients were defined as eligible for HFRT based on the American Society for Radiation Oncology (ASTRO) consensus guidelines and randomised trial testing intensity modulated and partial organ radiotherapy following breast conservation surgery for early breast cancer (IMPORT LOW) trial criteria, APBI based on the ASTRO, American Brachytherapy Society and the Groupe Européen de Curiethérapie of European Society for Therapeutic Radiotherapy and Oncology (GEC-ESTRO) consensus guidelines, and GEC-ESTRO APBI and IMPORT LOW trial criteria, and ET alone based on the Cancer and Leukemia Group B 9343 and Post-operative Radiotherapy in Minimum Risk Elderly II inclusion criteria. Results: A total of 108,484 women with early stage breast cancer who met the aforementioned inclusion criteria were identified. Of these patients, 86,896 (80.1%) were eligible for HFRT based on ASTRO consensus guidelines and 81,459 (75.0%) based on IMPORT LOW trial criteria. Regarding APBI, 44,797 (41.2%), 81,020 (74.6%), 81,020 (74.6%) were eligible according to ASTRO, ABS, GEC-ESTRO consensus guidelines, respectively, 97,301 (89.7%) patients according to the GEC-ESTRO trial criteria, and 81,459 (75.0%) patients according to the IMPORT LOW trial criteria. For ET alone, 23,006 (21.2%) were eligible according to Cancer and Leukemia Group B 9343 criteria and 42,104 (38.8%) according to Post-operative Radiotherapy in Minimum Risk Elderly II criteria. Conclusions: This SEER analysis demonstrates that a substantial proportion of women with early stage breast cancer are eligible for HFRT, APBI, or ET alone after breast conserving surgery according to consensus guidelines and prospective trial criteria. With incorporation of additional pathologic, dosimetric, and chemotherapy data, quality assurance pathways may use such data to help ensure patients are receiving appropriate risk stratified treatment recommendations.