Response to neoadjuvant chemotherapy in histologic variants of bladder cancer.

Abstract

458 Background: Localized muscle invasive bladder carcinoma is mostly treated with neoadjuvant chemotherapy (NAC) before surgery in order to improve the outcome. Urothelial carcinoma (UC) is the most frequent histological type. Histological variants (pure or mixed) occur in 10% of bladder carcinoma. There is a lack of data on NAC efficacy for these histological subtypes. In this study, we evaluated the histologic response to NAC in the variant population of bladder cancer. Methods: Patients from 2 french hospitals (CHU de Nantes and ICM) treated with NAC for bladder cancer from 2010 to August 2021 were included in this retrospective study. We compared response to NAC between UC and histologic variants (pure or mixed) on cystectomy piece. The histological response was defined by the tumor downstaging after NAC (≤pT1Nx). We also collected the pathological complete response (pCR), which was defined by no residual tumor on the cystectomy piece. Results: 87 patients were included. 31 patients harbored a variant pattern: 7 squamous component, 3 adenocarcinoma component, 5 micropapillary component, 2 sarcomatoid component, 4 neuroendocrine carcinoma, 4 nest, 1 lymphoepithelial carcinoma, 2 giant cell, 1 undifferentiated, 1 micropapilallary and adenocarcinoma component and 1 adenosquamous component; 56 were conventional UC. NAC was MVAC in 77% of patient in the variant group, and 82% in the UC group. Others chemotherapy drugs were used as gemzar cisplatine, and platine etoposide. Downstaging was observed in 55% of patients in the variant group (17/31) and in 59% in the UC group (33/56). The difference was not statistically significant (p <0,44). pCR was observed in 39% of patients in the variant group (12/31) and 43% in the UC group (24/56), the difference was not significant (p< 0.44). Conclusions: NAC can be effective in the histologic variant population of bladder carcinoma, nevertheless these data could be confirmed in a larger cohort.