Pretreatment tumour immune microenvironment predicts clinical response and prognosis of muscle-invasive bladder cancer in the neoadjuvant chemotherapy setting.

<bold>Background: </bold>We examined the relationship between the tumour microenvironment and the clinical efficacy of neoadjuvant chemotherapy in patients with cT2-4aN0M0 bladder cancer using multiplex fluorescence immunohistochemistry.<bold>Methods: </bold>The study retrospectively evaluated 51 patients who underwent radical cystectomy following neoadjuvant chemotherapy for cT2-4aN0M0 muscle-invasive bladder cancer. Patients were divided into responders (<pT2) and non-responders (≥pT2). We assessed the density of each immune cell type in intratumoural and peritumoural areas in both groups via multiplex fluorescence immunohistochemical analysis.<bold>Results: </bold>The median age was 69 years; 39 patients were male. Twelve (23.5%), 17 (33.3%), 10 (19.7%) and 12 (23.5%) patients were pT0, pT1, pT2 and ≥pT3, respectively. Responders had a significantly higher 5-year cancer-specific survival rate (96.6%) than non-responders (48.4%; p = 0.0018). CD8+ T cell (p = 0.0056) and CD204+ cell (p = 0.0394) densities were significantly higher in the intratumoural area in non-responders than in responders. Patients with higher CD204+ cell densities in cancerous areas had worse prognosis.<bold>Conclusions: </bold>This comprehensive analysis of the immune microenvironment of a muscle-invasive bladder cancer specimen revealed that preexisting tumour-infiltrating proliferating CD8+ T cells and CD204+ cells are indicators of the response to neoadjuvant chemotherapy and that CD204+ cells can be considered an unfavourable prognostic factor in these patients. [ABSTRACT FROM AUTHOR]