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 deatth 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.