Association of FGFR alterations with FGFR 1-4 gene expression in TUR biopsies and matched NMP22 urine levels in early bladder cancer of the prospective real world clinico-pathological register trial: BRIDGister.
Authors: Ralph M. Wirtz, Frank Friedersdorff, Elke Veltrup, Ergin Kilic, Richard Watts, Ronny Kellner, Roland Hake, Sebastian Eidt, Jenny Roggisch, Stefan Koch, Thorsten Ecke
Journal: Journal of Clinical Oncology (2021)

e16533 Background: The objective of the present study was to identify molecular charactersitics associated with FGFR positive tumors in matched urine and TUR biopsy samples from patients being suspicious of bladder cancer and undergoing first TURB at the pilot center of the multicentric BRIDGister Real World Experience trial that are helpful for patient management and prognosis. Methods: For this pilot study paraffin fixed pretreatment tissue samples from the first TURB of 28 pts participating in the BRIDGister trial and matched urine samples were prospectively collected and analyzed. RNA from FFPE tissues were extracted by commercial kits and analyzed by Therascreen FGFR IVD kit (Qiagen GmbH, Hilden). Relative gene expression of subtyping markers (KRT5, KRT0) as well as FGFR1, FGFR2, FGFR3, FGFR4, ERBB2 was centrally tested by standardized test systems (STRATIFYER Molecular Pathology GmbH, Cologne). In addition urine samples were analyzed by commercially available urine tests (UBC Rapid, BTA stat, NMP22). Spearman correlation, Kruskal-Wallis, MannWhitney and Sensitivity/Specificity tests were done by JMP 9.0.0 (SAS software). Results: The pilot cohort of the BRIDGister trial consisted of 28 patients (median age: 73, male 71% vs female 29%) of diverse clinical stages (Benign lesions/no tumor 21%, pTa 32%, pT1 21%, pT2 21%) and WHO 1973 grade (G1 7%, G2 43%, G3 21%). Based on FFPE tissue testing using Therascreen FGFR IVD kit 9 out of 28 patients exhibited FGFR alterations (32%). FGFR positive tumors were associated with high expression of FGFR3 mRNA (r = 5.951, p = 0.0011) but low FGFR1 mRNA as well as FGFR4 mRNA (r = -0.3882, p = 0.0412 and r = -0.6305, p = 0.0004, respectively). Interestingly, FGFR alteration was positively associated with the basal marker KRT5 (r = 0.3929, p = 0.0386), but not with luminal KRT20 mRNA expression (r = -0.0208, p = 0.9179). Moreover FGFR3 altered bladder cancer was associated with elevated NMP22 levels in pretreatment urine (r = 0.3978, p = 0.0361). Conclusions: In early bladder cancer FGFR3 alterations are tightly associated with a characteristic FGFR mRNA signature. Mutation/Fusion of FGFR3 results in high FGFR3 but low FGFR1 and FGFR4 mRNA expression, which might be i.a. relevant for the response to FGFR inhibition and important to predict outcome of FGFR inhibitors. Morever FGFR alteration was associated with elevated NMP22 urine levels, which might be helpful for detecting and monitoring FGFR altered bladder cancer in a non invasive fashion. These results warrant further investigation and its impact on outcome prediction (BCG responsiveness, recurrence, proegression, etc) will be prospectively analyzed in the framework of the ongoing multicenter BRIDGister Real World Experience trial.