Influence of lamina propria invasion extension on T1 high-grade non-muscle-invasive bladder cancer in patients undergoing BCG or radical cystectomy

Objective To evaluate the prognostic value of T1 substaging in patients treated with bacillus Calmette-Guerin (BCG) or immediate radical cystectomy (iRC). Materials and Methods We performed an institutional review board-approved retrospective study analysing non-muscle-invasive bladder cancer (NMIBC) patients with pT1 disease treated with either BCG or iRC between 2000 and 2020. Lamina propria (LP) invasion characteristics were extracted from the pathology report. The Kaplan-Meier method was used to calculate overall survival (OS), cancer-specific survival (CSS) and metastasis-free survival (MFS). Multivariable Cox models were used to determine the association between progression-free survival (PFS) and characteristics in the BCG cohort. A logistic regression model explored the relationship between T1 substaging and upstaging to >pT2 at iRC. Results A total of 411 T1 high-grade patients were identified. LP invasion characteristics were as follows: not specified: 115 (28%); focal/superficial (F/S): 147 (35.8%); and extensive/multifocal (E/M): 149 (36.2%). Overall, 303 patients (73.7%) received BCG, and 108 patients (26.3%) underwent iRC. The median (interquartile range) follow-up was 53 (32-96) months. Patients with E/M LP invasion were significantly more likely to undergo iRC (34% vs. 19%; P = 0.003). Patients with E/M LP invasion showed poorer MFS and CSS compared to those with F/S LP invasion when treated with BCG but not when treated with iRC. Among BCG-treated patients, progression occurred in 41 patients and E/M LP invasion was independently associated with progression after BCG (hazard ratio 5.3, 95% confidence interval [CI] 2.2-13.1; P < 0.001). T1 substaging was not associated with upstaging at RC (odds ratio 3.15, 95% CI 0.82-12.12; P = 0.095). Conclusions Extensive/multifocal LP invasion was associated with poor PFS, MFS and CSS in patients treated with BCG. T1 substaging provides valuable prognostic information and should be reported in pathology reports.