Background: Breast-conserving surgery with adjuvant radiotherapy and mastectomy are currently offered as equivalent surgical options for early-stage breast cancer based on RCTs from the 1970s and 1980s. However, the treatment of breast cancer has evolved and recent observational studies suggest a survival advantage for breast-conserving surgery with adjuvant radiotherapy. A systematic review and meta-analysis was undertaken to summarize the contemporary evidence regarding survival after breast-conserving surgery with adjuvant radiotherapy versus mastectomy for women with early-stage breast cancer.

Methods: A systematic search of MEDLINE, the Cochrane Central Register of Controlled Trials (CENTRAL), and Embase that identified studies published between 1 January 2000 and 18 December 2023 comparing overall survival after breast-conserving surgery with adjuvant radiotherapy versus mastectomy for patients with unilateral stage 1-3 breast cancer was undertaken. The main exclusion criteria were studies evaluating neoadjuvant chemotherapy, rare breast cancer subtypes, and specific breast cancer populations. The ROBINS-I tool was used to assess risk of bias, with the overall certainty of evidence assessed using the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) tool. Studies without critical risk of bias were included in a quantitative meta-analysis.

Results: From 11 750 abstracts, 108 eligible articles were identified, with one article including two studies; 29 studies were excluded from the meta-analysis due to an overall critical risk of bias, 42 studies were excluded due to overlapping study populations, and three studies were excluded due to reporting incompatible results. A total of 35 observational studies reported survival outcomes for 909 077 patients (362 390 patients undergoing mastectomy and 546 687 patients undergoing breast-conserving surgery with adjuvant radiotherapy). The pooled HR was 0.72 (95% c.i. 0.68 to 0.75, P < 0.001), demonstrating improved overall survival for patients undergoing breast-conserving surgery with adjuvant radiotherapy. The overall certainty of the evidence was very low.

Conclusion: This meta-analysis provides evidence suggesting a survival advantage for women undergoing breast-conserving surgery with adjuvant radiotherapy for early-stage breast cancer compared with mastectomy. Although these results should be interpreted with caution, they should be shared with patients to support informed surgical decision-making.