[Mutation of the FGFR3 oncogene is an independent and favorable prognostic factor for tumor-specific survival in patients with urothelial carcinoma of the upper urinary tract].

AIMS: Urothelial tumors of the upper urinary tract (UUTT) frequently display microsatellite Instability (MSI) and a distinct pathway of tumorigenesis resembling MMR-deficient colorectal cancers has been recognized for MSI-UUTT. For MSS-UUTT however oncogenic mechanisms as in bladder cancer (BC) are debated. Mutation of the oncogene FGFR3 has been linked to lower stage, lower grade and favourable clinical outcome in BC. The aim of this study was to evaluate FGFR3 mutation in MSI and MSS-UUTT. METHODS: 172 unselected UUTT were screened for MSI using the National Cancer Institute Consensus Panel and additional markers; FGFR3 status was studied using mutation analysis. Histopathological and clinical data were reviewed. RESULTS: Microsatellite status had no impact on histopathological or clinical outcome. 52/99 MSS, 10/22 MSI-low and 25/51 MSI-high UUTT displayed mut. FGFR3 respectively. Overall FGFR3 mutation was associated with favourable stage and grade (p <0.0001 and p <0.002), as 62.1% of mut. vs. 23.5 % of wt. FGFR3 UUTT were stage Ta and T1 and graded G3 in 25.3 % vs. 47.1% respectively. That effect depended on MS-status however, as FGFR3 mutation was related to lower stage (pTa and pT1) in MSS/MSI-L (mut 62.9 % vs. wt 18.7%; p <0.01) only as opposed to MSI-H (mut 60% vs. wt. 50%; p = 0,1) UUTTs and as FGFR3 mut UUTTs tended to display lower grade (G1 and G2) provided stable (mut 74,2 % vs. wt. 44.1%; p <0,01) as opposed to instable microsatellite status (mut 76 % vs. wt. 73 %; p = 0.7). There was no marked relation of MS-status or FGFR3 mutation to sex, age or tobacco-exposure; localization in the renal pelvis (p < 0.01) however was more prevalent in the FGFR3 mut group. As opposed to MSI-status FGFR3 mutation had a favourable impact on survival, as 24.1% vs. 54.2 % cancer related deaths occured in the mutated group (p