Recurrence and Mortality after Breast-Conserving Surgery without Radiation

Background: Breast-conserving surgery (BCS) and radiation therapy (RT) are the standard of care for early breast cancer; studies have demonstrated that adjuvant RT confers a protective effect with respect to recurrence, although no randomized trials have shown a survival benefit. Methods: This retrospective cohort study used Ontario data linked through ICES to examine patients treated for breast cancer between 1 April 2007 and 31 March 2014. The primary outcome was death or recurrence. Outcomes were compared between patients who did and did not receive RT. Results: The total cohort size was 26,279. The hazard ratios (HRS) for various outcomes were significantly higher for patients who did not receive RT than for patients who did: recurrence or death combined [HR: 2.49; 95% confidence interval (CI): 2.25 to 2.75], recurrence (HR: 2.33; 95% CI: 1.91 to 2.84), and death (HR: 2.28; 95% CI: 2.03 to 2.56). The HR for death was 1.81 (95% CI: 1.65 to 1.99) for patients having stage II cancer compared with those having stage I disease. The HR for death was 1.97 (95% CI: 1.74 to 2.22) for patients having high comorbidity compared with those having little comorbidity. Conclusions: Adjuvant RT carries a protective effect with respect to recurrence and survival in patients with early-stage breast cancer. That survival benefit has not been appreciated in previous randomized trials and underscores the importance of rt as a component of breast cancer treatment.