Stromal Tumor-Associated Macrophage Infiltration Predicts Poor Clinical Outcomes in Muscle-Invasive Bladder Cancer Patients

Background This study aims to reveal the clinical significance of stromal-infiltrating tumor-associated macrophages (TAMs) in muscle-invasive bladder cancer (MIBC). Patients and Methods This study included 288 patients from the TCGA database and 118 patients from Fudan University Shanghai Cancer Center with MIBC. The CIBERSORT model and immunohistochemistry were used to evaluate TAM infiltration. Cox regression analyses were employed to calculate their prognostic value. Results Among all 23 immune phenotypes analyzed in the TCGA cohort, pan-macrophage infiltration was significantly associated with poor prognosis ( p = 0.001). Further analyses found that stromal TAM infiltration could be an independent prognostic predictor for recurrence-free survival (RFS; HR: 1.019, 95% CI: 1.006–1.033, p = 0.004). High stromal infiltration was related to unfavorable RFS. After stratification by adjuvant chemotherapy (ACT), patients without ACT could be differentiated by TAM infiltration ( p = 0.036), while patients with ACT could not. Moreover, TAM infiltration was negatively associated with IFN-γ-related mRNA panel, which was shown to have strong predictive value for clinical response to programmed death-1 (PD-1) inhibition. Conclusions Stromal TAM infiltration could be an independent prognosticator for MIBC patients. This might have potential to guide precise treatments such as ACT and immune checkpoint blockade in MIBC.