FGFR3 gene mutations screening in non-muscle invasive bladder cancer (NMIBC) in the Tunisian population

Background Mutations occurring in the Fibroblast Growth Factor Receptor (FGFR3) gene are thought to be associated with the incidence and prognosis of non-muscle invasive bladder tumors (NMIBC). Yet, their prognostic significance in the Tunisian population remains unclear. Herein, we aim to investigate their prognostic impact in NMIBC in terms of recurrence, progression, and survival. Methods and results It is a monocentric retrospective study including 42 NMIBC patients. DNA was isolated from formalin-fixed paraffin-embedded tissue samples. Polymerase Chain Reaction (PCR) followed by Sanger sequencing were performed for a targeted mutations' screening of the hot-spot regions of the FGFR3 gene (exons 7 and 15). Overall survival (OS) and disease-specific survival (DSS) were estimated by the Kaplan-Meier method and the corresponding curves were compared using log-rank test. Sequencing analysis revealed 15 different mutations in FGFR3 gene across 26 different tumors (68%). Among these, 9 are already reported mutations (S249C, P250R, P250S, H251Q, S249S, S249Y, S249A, T264T, Thr651) and, interestingly, 6 are new variants (P250A, H251L, A257S, P253P, I254V, R618S). FGFR3-mutated NMIBC and wild-type FGFR3 tumors were comparable in terms of clinical and endoscopic presentation. The presence of FGFR3 mutations was not statistically correlated to a decrease in OS and DSS. The main factors correlated with their presence were the solid appearance of the tumor (p = 0.04), the presence of tumor calcifications (p = 0.04), and tumor stage (p = 0.04). Conclusion FGFR3 mutations were common in our series. These variations seem to be a favorable prognostic factor for NMIBC in our population.