Tumor infiltrating M2 macrophages could predict biochemical recurrence of localized prostate cancer after radical prostatectomy.

Given the critical role of the tumor microenvironment in PCa progression, we aimed to assess the prognostic effect of tumor infiltrating M2 macrophages (TIMMs) on biochemical recurrence (BCR) in patients with localized prostate cancer (PCa) after radical prostatectomy. A total of 127 localized PCa patients from GSE116918, 268 patients from TCGA database and 77 patients from GSE70770 were enrolled in our study. TIMMs were evaluated by the CIBERSORT method. Patients with high TIMMs had a significantly poorer recurrence free survival (RFS) (P = 0.017, P = 0.0063 and P = 0.001) in the three sets. In the multivariate analysis, the presence of high TIMMs (HR = 3.026, P = 0.023; HR = 2.679, P = 0.017; HR = 2.648, P = 0.005) was identified as an independent prognostic factor for RFS in the three sets. Harrell's Concordance index (C-index) increased in all three sets after combining TIMMs with traditional risk factors (PSA, clinical stage(T) and Gleason score). Gene Set Enrichment Analysis showed that T cell receptor signaling pathway, B cell receptor signaling pathway and primary immunodeficiency were significantly enriched in the low TIMMs group. TIMMs could serve as an independent prognostic factor for BCR in localized PCa patients after RP. Incorporation of TIMMs into traditional risk classification might further stratify patients with different prognosis.