Metric substage according to micro and extensive lamina propria invasion improves prognostics in T1 bladder cancer

Reliable prognosticators for T1 bladder cancer (T1BC) are urgently needed.

To compare the prognostic value of 2 substage systems for T1BC in patients treated by transurethral resection (TUR) and adjuvant bacillus Calmette-Guérin therapy.

The slides of 601 primary T1BCs from four institutes were reviewed by 2 uropathologists and substaged according to 2 classifications: metric substage according to T1 microinvasive (T1m-lamina propria invasion <0.5mm) and T1 extensive invasive (pT1e-invasion ≥ 0.5mm), and according to invasion of the muscularis mucosae (MM) (T1a-invasion above or into MM/T1b).

Multivariable analyses for progression-free (PFS) and cancer-specific survival (CSS) were performed including substage, size, multiplicity, carcinoma in situ, sex, age, WHO-grade 1973, and WHO-grade 2004 as variables.

Median follow-up was 5.9 years (interquartile range: 3.3-9.0). Progression to T2BC was observed in 148 (25%) patients and 94 (16%) died of BC. The MM was not present at the invasion front in 135 (22%) of tumors. Slides were substaged as follows: 213 T1m and 388 T1e and 281 T1a and 320 T1b. On multivariable analysis, T1m/e substage and WHO 1973 grade were the strongest prognosticators for PFS (hazard ratio [HR] = 3.8 and HR = 1.8) and CSS (HR = 2.7 and HR = 2.6), respectively. Other prognostic factors for CSS were age (HR = 1.03), and tumor size (HR = 1.8). Substage according to MM-invasion was not significant. Our study was limited by its retrospective design and that standard re-TUR was not performed if TUR was macroscopically complete and muscularis propria was present in resected specimens.

Metric substaging of T1BC was possible in all cases of 601 T1BC patients and it was a strong independent prognosticator of both PFS and CSS.