Prognostic significance of tumor-associated macrophages in ovarian cancer: A meta-analysis

Objective The role of tumor-associated macrophages (TAMs) in tumor microenvironment remains controversial due to the two different polarized subsets of TAMs. Here, we performed a meta-analysis to evaluate the correlation between subpopulations of TAMs and clinical outcomes in patients with ovarian cancer. Methods A comprehensive search in PUBMED/Medline and EMBASE databases was performed. The association between TAMs and patient prognosis of ovarian cancer was estimated with hazard ratios (HRs) and their corresponding 95% confidence intervals (95% CIs) using a random-effect model. Additionally, sensitivity analysis and Begg's test were conducted. Results Nine studies including 794 patients were enrolled in the meta-analysis. The results showed that higher M1/M2 ratio in tumor tissues was associated with a favorable overall survival (OS) (HR = 0.449, 95% CI = 0.283–0.712, P = 0.001). Elevated intra-islet M1/M2 TAMs ratio showed a positive correlation for OS (HR = 0.510, 95% CI = 0.264–0.986, P = 0.045). No significant relation was observed between OS and CD68+ TAMs (HR = 0.99, 95% CI = 0.88–1.11, P = 0.859), CD163+ TAMs (HR = 1.04, 95% CI = 0.92–1.16, P = 0.544) or CD163+/CD68+ TAMs ratio (HR = 1.628, 95% CI = 0.529–5.008, P = 0.395). Worse progression-free survival (PFS) was associated with high density of CD163+ TAMs (HR = 2.157, 95% CI = 1.406–3.312, P = 0.000) and higher ratio of CD163+/CD68+ TAMs (HR = 3.223, 95% CI = 1.805–5.755, P = 0.000). Elevated M1/M2 TAMs ratio predicted better PFS of ovarian cancer (HR = 0.490, 95% CI = 0.270–0.890, P = 0.019). Furthermore, high density of CD163+ and CD68+ TAMs was observed in ovarian cancer with advanced TNM stage. Conclusion In our study, it was revealed that CD163+ TAMs infiltration was associated with poor prognosis of ovarian cancer and high M1/M2 macrophages ratio in tumor tissues predicted better prognosis.