Identification of the Tumor Infiltrating Lymphocytes (TILs) Landscape in Pure Squamous Cell Carcinoma of the Bladder

Simple Summary Treatment options in squamous cell carcinoma (SCC) of the bladder are limited and prognosis is poor. In this report we investigated the impact of tumor-infiltrating lymphocytes (TILs) in SCC of the bladder in patients undergoing radical cystectomy. We found that subsets of TILs hold predictive value for OS and PFS. We conclude that TILs might stratify patients with bladder SCC for immunotherapy. Background: Tumor infiltrating lymphocytes (TILs) are known as important prognostic biomarkers and build the fundament for immunotherapy. However, the presence of TILs and its impact on outcome in pure squamous cell carcinoma (SCC) of the bladder remains uncertain. Methods: Out of 1600 patients undergoing radical cystectomy, 61 patients revealed pure bladder SCC in the final histopathological specimen. Retrospectively, immunohistochemical staining was performed on a subset of TILs (CD3+, CD4+, CD8+, CD20+). Endpoints were overall survival (OS), cancer-specific survival (CSS) and progression-free survival (PFS). The Kaplan-Meier method was used to evaluate survival outcomes. Results: Strong infiltration of CD3+ was found in 27 (44%); of CD4+ in 28 (46%); of CD8+ in 26 (43%); and of CD20+ in 27 tumors (44%). Improved OS was observed for strong CD3+ (p < 0.001); CD4+ (p = 0.045); CD8+ (p = 0.001); and CD20+ infiltration (p < 0.001). Increased rates of PFS were observed for CD3+ (p = 0.025) and CD20+ TILs (p = 0.002). In multivariate analyses, strong CD3+ (HR: 0.163, CI: 0.044-0.614) and strong CD8+ TILs (HR: 0.265, CI: 0.081-0.864) were revealed as predictors for OS and the strong infiltration of CD20+ cells (HR: 0.095, CI: 0.019-0.464) for PFS. Conclusions: These first results of TILs in bladder SCC revealed predictive values of CD3+, CD8+ and CD20+.