A new and highly prognostic system to discern T1 bladder cancer substage

Background: Management of T1 bladder cancer (BCa) is controversial.

Objective: Evaluate the impact of substage on the clinical outcome of T1 BCa.

Design, setting, and participants: The T1 diagnosis of 134 first-diagnosis BCa patients from two university hospitals was confirmed. For the T1 substage, we used a new system that discerns T1-microinvasive (T1m) and T1-extensive-invasive (T1e) tumors. We then determined the invasion of the muscularis mucosae-vascular plexus (MM-VP): T1a (invasion above the MM-VP), T1b (invasion in the MM-VP), or T1c (invasion beyond the MM-VP). If the MM-VP was not present at the invasion front, the case was assigned to T1a or T1c. All patients were initially managed conservatively (with bacillus Calmette-Guérin).

Measurements: Multivariable analyses for progression and disease-specific survival (DSS).

Results and limitations: Median follow-up was 6.4 yr (interquartile range: 3.3-9.2 yr). Progression to ≥ T2 was observed in 40 patients (30%), and 19 patients (14%) died of BCa. The MM-VP was not present at the invasion front in 50 patients (37%). T1 substage was as follows: 40 T1m and 94 T1e; 81 T1a, 18 T1b, and 35 T1c. In multivariable analyses, substage (T1m/T1e) was significant for progression (p=0.001) and DSS (p=0.032), whereas substage according to T1a/T1b/T1c was not significant. Female gender (p=0.006) and carcinoma in situ (p=0.034) were also significant predictors of progression. The main limitation to the study is absence of a repeat transurethral resection.

Conclusions: Substage according to the new system (T1m and T1e) was user-friendly, possible in 100% of cases, and very predictive of T1 BCa behavior. Future studies may ultimately lead to the incorporation of this new substaging system in the TNM classification system for urinary BCa.