Circulating Tumor Cells and Radiotherapy Benefit in Early Breast Cancer

To the Editor Goodman et al¹ recently described a consistent benefit from radiotherapy (RT) in terms of survival and distant disease control after breast-conserving surgery (BCS), but not mastectomy, in 2 cohorts of patients with breast cancer (BC) harboring any circulating tumor cells (CTCs). Speers and Rugo² emphasize that the lack of benefit from RT in patients with CTC-negative status is probably owing to the study being underpowered to detect small benefits, and the findings should not be regarded as contradictory to abundant randomized evidence of the benefit of RT. We agree and value the identification of a predictive biomarker of RT benefit.