Objective In this study, a meta-analysis of the expression of G-protein-coupled estrogen receptor (GPER) in breast cancer (BC) and its role in prognosis was conducted to understand the effect of this expression on the survival and clinicopathological characteristics of patients with BC.

Methods Identical search strategies were used to search relevant literature in electronic databases updated to November 24, 2022. Individual hazard ratios (HRs) and odds ratios (ORs) with their 95%CI were extracted and pooled to evaluate the strength of the association between positive GPER expression and survival results, the clinicopathological features of patients with BC. Begg's tests, Egger's tests, and funnel plots were used to evaluate publication bias. Heterogeneity and sensitivity were also assessed. All works were completed using Review Manager 5.4.1.

Results GPER expression had a favorable effect on OS (HR=0.77; 95%CI: 0.49-1.22; Z=01.10; P=0.27) and an unfavorable effect on DFS/RFS/DDFS (HR=1.03; 95%CI: 0.64-1.65; Z=00.13; P=0.90) in patients with BC. GPER expression was not significantly related to the prognosis of patients with BC, and GPER expression was not an independent prognostic factor. Furthermore, GPER expression was significantly associated with TNM staging (OR=0.31, 95%CI: 0.06-0.55, Z=02.43, P=0.02), distant metastasis (OR=6.82, 95%CI: 1.89-24.55, Z=02.94, P=0.003), histological grade (OR=0.009, 95%CI: −0.16-0.01, Z=02.16, P=0.03), ER expression (OR=1.77, 95%CI: 1.15-2.72, Z=02.59, P=0.009), and PR expression (OR=1.36, 95%CI: 1.00-1.84, Z=01.95, P=0.05).

Conclusion GPER may not be an independent prognostic factor for BC. GPER expression was significantly related to some clinicopathological features of patients with BC, including TNM staging, distant metastasis, histological grade, ER expression, and PR expression.