Validation of new AJCC exclusion criteria for subepithelial prostatic stromal invasion from pT4a bladder urothelial carcinoma

Purpose: In 2010 the AJCC (American Joint Committee on Cancer) excluded urothelial carcinoma with subepithelial prostatic stromal invasion from the pT4a bladder cancer staging class, which is otherwise defined by direct prostatic invasion transmurally from the bladder. We determined if the new guidelines were reflective of differences in survival between subepithelial prostatic stromal invasion and transmural pT4a disease. Materials and Methods: A retrospective, multi-institutional cohort of cystectomy cases with subepithelial prostatic stromal invasion from the University of Chicago and Cleveland Clinic were compared to a cohort with transmural pT4a disease. All pathological specimens were rereviewed at the respective institutions. Patients were excluded from the final cohort if variant bladder cancer histology, pT3 bladder disease or extraprostatic extension of urothelial carcinoma were identified. The primary end points were cancer specific and overall survival. Results: Our study sample consisted of 48 patients with subepithelial prostatic stromal invasion and 49 patients with transmural pT4a disease. Median followup was 12.8 months (IQR 4.9 to 31.4). Patients with subepithelial prostatic stromal invasion had lower rates of lymph node involvement than those with transmural pT4a disease (14.6% vs 61.2%, p <0.001) and lower rates of positive surgical margins (18.7% vs 61.2%, p <0.001). Rates of perioperative chemotherapy were similar in both groups. When comparing subepithelial prostatic stromal invasion and transmural pT4a groups, overall survival was 64.0 vs 9.8 months and median cancer specific survival was not achieved vs 16.5 months, respectively (p <0.001). Conclusions: Subepithelial prostatic stromal invasion from urothelial carcinoma has more favorable outcomes compared to transmural pT4a disease. Our results support the exclusion of subepithelial prostatic stromal invasion from the pT4a bladder urothelial carcinoma staging class.