Prognostic significance of occult lymph node metastases in breast cancer: a meta-analysis

Background Occult metastases in axillary lymph nodes have been reported to be associated with poor prognosis in patients with breast cancer. However, studies on the prognostic value of occult metastases have shown controversial results. This meta-analysis aimed to evaluate the prognostic significance of occult lymph node metastases in breast cancer. Methods Studies published until May, 2020, which retrospectively examined negative lymph nodes by stepsectioning and/or immunohistochemistry, were retrieved from MEDLINE, EMBASE, CNKI, and Cochrane Library databases. The pooled Relative Risk (RR) with 95% confidence interval (95% CI) for overall survival (OS) and disease-free survival (DFS) were calculated to examine the associations between occult metastases and prognosis. Results Patients with occult metastases in axillary lymph nodes had poorer five-year DFS (RR = 0.930; 95% CI = 0.907-0.954) and OS (RR = 0.972; 95% CI = 0.954-0.990). Furthermore, the DFS (RR = 0.887; 95% CI = 0.810-0.972) and OS (RR = 0.896; 95% CI = 0.856-0.939) of patients with occult metastases were significantly lower after a ten-year follow-up. Conclusions Occult metastases in the axillary lymph nodes are associated with poorer DFS andOS of patients with breast cancer. Occult metastases might serve as a predictive factor of survival outcomes in patients with breast cancer. Keywords: Breast cancer, Occult metastases, Axillary lymph nodes, Survival, Recurrence