Outcome of Metastatic Biliary Tract Cancer Harbouring IDH1 or FGFR2 Alterations: A Retrospective Observational Real-World Study from a French Cohort

<b>Background</b>: Biliary tract cancer (BTC) management has undergone tremendous changes, benefiting from the identification of highly actionable molecular alterations. Among these, <i>IDH1</i> mutations and <i>FGFR2</i> fusions are the most common alterations detected and are classified as ESCAT tier 1 in BTC. However, their prognostic value in real-world settings remains uncertain. <b>Objective</b>: To explore overall survival (OS) in patients harbouring locally advanced or metastatic BTC (mBTC) with <i>IDH1</i> or <i>FGFR2</i> alterations, compared to those with wild-type tumours. <b>Methods</b>: This retrospective, multicentre study included patients with mBTC treated between 2020 and 2023 across five French centres. Patients were categorized into two cohorts based on molecular profiling: those with <i>IDH1</i> or <i>FGFR2</i> alterations, and those with wild-type tumours (WT-mBTC). <b>Results</b>: 119 consecutive patients were included. 18 were classified as altered (<i>IDH1</i> = 13; <i>FGFR2</i> = 5). Sixty-four pts underwent no molecular testing. The median OS of the entire cohort was 11.9 months (10.3-14.3). The median OS was 24.2 months (12.3-NA) versus 10.8 months (7.9-12.9), <i>p</i> = 0.02, in the altered and WT-mBTC cohorts, respectively. The Cox regression model conducted depicted an HR for death of 0.46 (CI95%, 0.2-0.9) for <i>IDH1</i> or <i>FGFR2</i> alterations. There were no diffence in PFS for first-line. <b>Conclusions</b>: Our cohort suggests that IDH1 or FGFR2 alterations may be associated with prognostic differences in patients with metastatic BTC, although they do not appear to influence outcomes under first-line treatment. These findings are consistent with trends observed in clinical trials. Whether improved survival is solely attributable to targeted therapies remains questionable. In line with ESMO recommendations, systematic molecular profiling should be considered in patients with mBTC.