Substaging by estimating the size of invasive tumour can improve risk stratification in pT1 urothelial bladder cancer-evaluation of a large hospital-based single-centre series

Aims: The outcome of patients with pT1 bladder cancer cannot yet be reliably estimated. The aim of this study was to evaluate several parameters in one of the largest series of initial pT1 bladder cancers. Methods and results: Specimens of 309 patients with pT1 urothelial carcinoma were re-evaluated histologically, including size of infiltrating tumour area estimated as equal to or smaller than one high-power field (HPF) or larger than one HPF, and tumour infiltration in relation to the muscularis mucosae (pT1a/b). Results were correlated with clinical follow-up. Substaging by HPF was associated with tumour recurrence, progression and survival in univariate analysis, and with recurrence and progression in multivariate analysis. According to the World Health Organization (WHO) 1973 grading, 220 tumours were G3, 89 were G2, and none was G1. Tumour grading was an independent prognostic marker of survival. Substaging by HPF revealed G2 and G3 tumours as distinct prognostic groups with regard to recurrence and progression. No significance was found for substaging pT1a/pT1b. An infiltrative growth pattern was significantly correlated with progression and survival in univariate analysis. Conclusions: Comparison of two systems of substaging pT1 bladder cancer shows that measurement of the size of infiltrating tumour area by HPFs may improve risk stratification. An infiltrative growth pattern on the invasion front should be documented in the pathological report, indicating a worse outcome. Additional studies are needed to find further parameters detecting high-risk tumours.