Initial high-grade T1 urothelial cell carcinoma: feasibility and prognostic significance of lamina propria invasion microstaging (T1a/b/c) in BCG-treated and BCG-non-treated patients

OBJECTIVES: This study aimed to determine the prognostic value of depth of lamina propria invasion in initial high-grade T1 bladder tumors. Secondary aims were to evaluate the prognostic significance of concomitant carcinoma in situ (CIS) and the impact of bacillus Calmette-Guérin (BCG) treatment as well as to assess the feasibility of microstaging by pathologists in a community setting. PATIENTS AND METHODS: Ninety-seven tumors were available for study and were substaged according to invasion superficial to, into or beyond the muscularis mucosae (MM) (T1a, T1b, T1c). Outcomes were compared by chi-square analysis. Recurrence-free and progression-free survival estimates were obtained by Kaplan-Meier analysis. BCG treatment impact and prognostic significance of CIS were also evaluated (Cox regression). RESULTS: T1 subclassification was possible in 87% (85/97) of cases: 38 (39.1%) T1a, 10 (10.3%) T1b, and 37 (38.1%) T1c; in 12 patients (12.4%) substaging was not possible. Mean age was 66.4 years and mean follow-up was 53 months. Recurrence rates were similar for all groups. By contrast, the progression rate for deep lamina propria-invasive tumors, i.e. T1b and T1c, was 34% (16/47) in comparison to 8% (3/38) for T1a (p=0.016). Progression-free intervals were significantly different in patients with (T1b, T1c) or without (T1a) deep lamina propria involvement (p=0.003), regardless of BCG treatment (p=0.02). BCG-treated patients (67 cases) showed a slight trend towards a better outcome, but differences were not significant. CIS was associated with more than 50% of cases that progressed. On multivariate analysis, depth of invasion and CIS remained two independent prognostic factors, increasing the hazards ratio of progression to 4.47 and 3.19 respectively. CONCLUSIONS: The depth of invasion in the TURB specimens is an independent prognostic factor for T1 bladder cancer even in BCG-treated patients. Associated CIS significantly increases the risk of progression in these patients. The percentage of cases that can be substaged according to the depth of lamina propria involvement increases over time with the collaboration between urologists and pathologists. Consequently, we support that routine pathological assessment of the level of MM invasion in patients with stage T1 bladder cancer should be included in the histopathological report.