A systematic review and meta-analysis 1 summarized the evidence regarding survival after breast-conserving surgery (BCS) with adjuvant radiotherapy vs mastectomy for women with early-stage breast cancer. 35 observational studies reported survival outcomes for 909 077 patients (n=362 390 with mastectomy and 546 687with breast-conserving surgery with adjuvant radiotherapy). The pooled HR was 0.72 (95% CI 0.68 to 0.75, P < 0.001), demonstrating improved overall survival for patients undergoing BCS with adjuvant radiotherapy. The overall certainty of the evidence was very low.
Another meta-analysis 2 assessing overall survival (OS) included 6 trials with a total of 22 598 patients 40 years old or younger with early T1-T2 N0-N + M0 breast cancer. 10898 patients underwent BCS plus whole breast radiotherapy and 11700 underwent mastectomy. No difference in risk of death was found between the two groups (10% not significant risk reduction in patients who underwent BCS compared to mastectomy) HR 0.90; 95% CI 0.81 to 1.00).
A population-based study 3 evaluated 10 year survival of 37 207 patients after BCS plus radiotherapy vs mastectomy. Primary outcomes were 10 year overall survival in the entire cohort and breast cancer-specific survival in a representative subcohort of patients diagnosed in 2003 with characteristics similar to the entire cohort. In the 2003 subcohort 62% received BCS plus radiotherapy and 38% received mastectomy. BCS plus radiotherapy was significantly associated with improved 10 year overall survival in the whole cohort overall compared with mastectomy: adjusted HR 0.81, 95% CI 0.78 to 0.85; p<0·0001, and this improvement remained significant for all subgroups of different T and N stages of breast cancer. BCS plus radiotherapy did not significantly improve 10 year distant metastasis-free survival in the 2003 cohort overall compared with mastectomy (adjusted HR 0.88. 95% CI 0.77 to 1.01; p=0.7), but did in the T1N0 subgroup.
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