Breast-conserving surgery with or without radiotherapy: Pooled-analysis for risks of ipsilateral breast tumor recurrence and mortality

Background: The objective of the study was to investigate whether radiotherapy or its omission after breast-conserving surgery has measurable consequences on local tumor growth and patient survival. Methods: We conducted a pooled analysis of published randomized clinical trials that compared radiotherapy versus no radiotherapy after breast-conserving surgery. The outcomes studied were ipsilateral breast tumor recurrence and patient death from any cause. The pooled relative risks (RRs) were estimated with a random-effects model. Heterogeneity was assessed using the Cochran Q test. Results: A search of the literature identified 15 trials with a pooled total of 9422 patients available for analysis. The relative risk of ipsilateral breast tumor recurrence after breast-conserving surgery, comparing patients treated with no radiotherapy or radiotherapy, was 3.00 (95% confidence interval [CI] = 2.65 to 3.40). Mortality data were available for 13 trials with a pooled total of 8206 patients. The relative risk of mortality was 1.086 (95% CI = 1.003 to 1.175), corresponding to an estimated 8.6% (95% CI = 0.3% to 17.5%) relative excess mortality if radiotherapy was omitted. Conclusion: Omission of radiotherapy is associated with a large increase in risk of ipsilateral breast tumor recurrence and with a small increase in the risk of patient mortality.