LAUSR

There is a growing literature on the significance of tumor-associated macrophages (TAMs) in colorectal cancer (CRC). However, the role of TAMs in predicting the prognosis of CRC remains controversial. The current study aims to determine the prognostic and clinicopathological value of different types and distribution of TAMs in CRC. A comprehensive literature search of PubMed, Embase, and Cochrane Library databases was conducted from the inception to 1 September 2019. The correlations of TAMs with overall survival (OS), disease-free survival (DFS), cancer-specific survival (CSS), and clinicopathological characteristics were analyzed. A total of 5,575 patients from 29 studies were included in this meta-analysis. The pooled hazard ratios (HRs) indicated that high density of pan-macrophages in tumor invasive margin (IM) was associated with better OS (HR = 0.57, 95%CI = 0.38–0.85), DFS (HR = 0.32, 95%CI = 0.19–0.52), and CSS (HR = 0.56, 95%CI = 0.41–0.77). Moreover, the high density of pan-macrophages in tumor center (TC) was correlated with better DFS (HR = 0.66, 95%CI = 0.45–0.96). However, high expression of M2 macrophages in TC was associated with poor DFS (HR = 2.42, 95%CI = 1.45–4.07) and CSS (HR = 1.74, 95%CI = 1.24–2.44). High M2 macrophages density in IM was also associated with short DFS (HR = 2.81, 95%CI = 1.65–4.77). In addition, the results showed that high density of pan-macrophages in IM was associated with no tumor metastasis, while high M2 macrophages density in TC was correlated with poor tumor differentiation. High Pan-TAMs density in IM has a positive effect on the prognosis of CRC patients, while high density M2 macrophage infiltration in TC is a strong indicator of poor prognosis.