Reassessing Evidence on Omitting Radiotherapy After Breast‐Conserving Surgery

Zhang and colleagues report that omitting radiotherapy (RT) after breast-conserving surgery increases local recurrence without affecting overall survival (OS) [1]. The meta-analysis pools invasive cancer and DCIS trials despite major biological and clinical differences, which may obscure disease-specific treatment effects [2, 3]. Endpoint definitions also dilute the direct impact of RT; disease-free survival included contralateral and non-breast primaries, as well as deaths without prior cancer events. Competing-risk approaches and STEEP-aligned invasive disease-free survival would provide clearer estimates. Hazard ratios were applied over very long follow-up even though time-varying effects are evident, with early local recurrence separation that attenuates later. Restricted mean survival time could better represent this temporal pattern [1]. Moreover, most trials date back to the 1980s–1990s, before modern systemic therapy, sentinel node staging, or conformal RT. Interpreting pooled “null OS” results from historical cohorts as evidence for current practice risks ecological fallacy [4, 5]. In summary, the study confirms RT's role in reducing local recurrence, but stronger disease-specific analyses, modern endpoint conventions, and era-appropriate interpretation are needed before concluding survival neutrality. The author has nothing to report. This letter highlights key methodological limitations in interpreting survival neutrality when radiotherapy is omitted after breast-conserving surgery.