Omission of radiotherapy after breast conservation surgery in the postneoadjuvant setting.

Background: Breast conservation therapy (BCT) consists of breast conservation surgery (BCS) and radiotherapy (RT). Neoadjuvant chemotherapy (NACT) can downstage tumors, broadening BCS eligibility in patients requiring mastectomy. However, tumor downstaging does not obviate need for RT. This study evaluated factors that predict RT omission after NACT and BCS.

Methods: The National Cancer Database was queried for women with unilateral, clinical stage II-III breast cancer, treated with NACT and BCS between 2008 and 2012. Patients not receiving RT after NACT and BCS were identified. A subgroup analysis was performed eliminating patients for whom RT was recommended but not received.

Results: Among 10,220 patients meeting study eligibility, 974 (9.53%) did not receive RT after BCS. Predictors of RT omission included older age, insurance status, facility type, facility region, more recent year of diagnosis, receptor status unknown, human epidermal growth factor receptor 2 status positive or unknown, and positive margins. Factors increasing the likelihood of RT receipt included cN3 disease, receptor positivity, and primary downstaging. Race, Hispanicity, education, income, comorbidities, rural versus urban setting, histology, grade, and nodal stage change were not associated with RT omission. When excluding the 314 patients for whom RT was recommended but not received, age, Medicaid insurance, facility type, facility region, receptor status unknown, human epidermal growth factor receptor 2 status unknown, and positive margins were predictors of RT omission.

Conclusions: Race, comorbidities, and socioeconomic status were not predictors of RT omission. It remains unclear whether omission of RT in some cases is due to lack of physician knowledge. Further efforts are needed to ensure that physicians and patients recognize that RT is a vital and required part of BCT, even after NACT.