Effect of post-mastectomy radiation therapy on survival in breast cancer with lymph nodes micrometastases: a meta-analysis and systematic review

Abstract

Background: Axillary management of patients with early-stage breast cancer (ESBC) has evolved, especially with the implementation of precision radiotherapy techniques that have resulted in a significant reduction in treatment-related toxicities, but it is unclear whether post-mastectomy radiotherapy (PMRT) improves survival outcomes in breast cancer with lymph nodes micrometastases (BCLNMM, that is T0, T1 ~2NmiM0). Our study is to systematically evaluate the effect of PMRT on survival in breast cancer with lymph nodes micrometastases. Methods: A literature search was performed for randomized controlled trials (RCTs) or retrospective studies related to PMRT versus non-post-mastectomy radiotherapy (non-PMRT) in the adjuvant treatment of ESBC in PubMed, Cochrane Library, Embase, CNKI and other databases. R package meta software was used to perform meta-analyses with hazard ratio (HR). Newcastle Ottawa scale was selected for quality assessment. The review was prospectively registered on PROSPERO (CRD42024562444). Results: 10 relevant studies were screened, all of which were retrospective studies. The difference in overall survival (OS) was not statistically significant (HR = 0.92, 95%CI: 0.81 ~ 1.04; Z = 1.35, P = 0.177). The difference in breast cancer-specific survival (BCSS) between the PMRT group and the non-PMRT group was not statistically significant HR = 1.18, 95%CI: 0.94 ~ 1.48; Z = 1.41, P =0.160). The difference in disease-free survival (DFS) was statistically significant (HR = 0.47, 95%CI: 0.23 ~ 1.00; Z = 1.96, P =0.049). The difference in local recurrence free survival (LRRFS) was also not statistically significant (HR = 0.50, 95%CI: 0.11 ~ 2.26, P = 0.190). The difference in distant-metastasis free survival (DMFS) was not statistically significant (HR = 0.54, 95%CI: 0.22 ~ 1.35, P = 0.356). Conclusions: Despite the tendency of PMRT in BCLNMM to improve DFS, OS, BCSS, LRRFS, and DMFS showed no benefit, therefore, PMRT should be used with caution in BCLNMM. Systematic review registration: https://www.crd.york.ac.uk/prospero/, identifier CRD42024562444.