An Immunohistochemistry-Based Molecular Subtyping Approach for Capturing Clinical Outcome Heterogeneity in Bladder...

Backgrounds: Bladder cancer shows pronounced biological heterogeneity that underlies its variable clinical course and prognosis. Our study aims to delineate clinically relevant differences in bladder cancer using an immunohistochemistry-based molecular subtyping approach. Methods: This retrospective study included 590 patients with bladder cancer treated at a single center. Tumors were stratified into luminal versus non-luminal categories according to CK20, GATA3, CK5/6, and CK14. Associations between molecular subtype, histopathological growth patterns, pathological response to neoadjuvant chemotherapy (NAC), and clinical survival endpoints were analyzed. Overall survival (OS), recurrence-free survival (RFS), and progression-free survival (PFS) were evaluated through Kaplan-Meier survival curves together with Cox proportional hazards regression analyses. Results: Non-luminal tumors exhibited significantly more aggressive pathological growth patterns, including higher levels of tumor budding (p = 0.002), a predominance of non-cohesive or spindle/single-cell architecture (p = 0.003), and more frequent disseminated spreading patterns (p = 0.001), whereas luminal tumors more commonly displayed a higher frequency of tertiary lymphoid structures (TLSs; p = 0.041). Among patients receiving NAC, non-luminal tumors achieved a significantly higher pathological complete response (pCR) rate compared with luminal tumors (p = 0.007), while no significant inter-subtype difference was detected in pathological downstaging between subtypes (p = 0.126). Despite inferior pathological response, luminal tumors demonstrated significantly improved OS (p = 0.003), RFS (p = 0.002) and PFS (p < 0.001) compared with non-luminal tumors. In multivariable Cox regression analysis, molecular subtype was identified as an independent predictor of OS, with luminal tumors showing a lower mortality risk (HR = 0.51, 95% CI 0.33-0.79, p = 0.003). Conclusions: These findings indicate that pathological response and long-term survival follow distinct, subtype-dependent trajectories in bladder cancer. Favorable pathological response does not necessarily correspond to improved long-term survival across molecular subtypes.