Real-world testing, treatment patterns, and outcomes following liquid biopsy in advanced cholangiocarcinoma.

Abstract

455 Background: Cholangiocarcinoma (CCA) is an aggressive cancer with a poor prognosis. Given failure rates of up to 27% of CCA tissue biopsies, liquid biopsy has become an important tool to identify actionable molecular alterations. It is estimated tissue-based testing identifies IDH1 mutations and FGFR2 fusions in 12% and 9% of patients with advanced CCA (aCCA), respectively. Here we examined the rate of molecular alteration detection using circulating tumor DNA (ctDNA) testing, treatment patterns in aCCA, and outcomes for patients receiving ivosidenib following ctDNA-detected IDH1 mutations. Methods: Real-world data was sourced from GuardantINFORM, which comprises aggregated commercial payer health claims and de-identified records from >330,000 patients with clinical ctDNA testing via Guardant360 (G360), from 2014 to 2023. Patients with aCCA and >1 treatment claim after G360 results were included (N=1726). Patient outcomes were assessed via real-world time to treatment discontinuation (rwTTD), real-world time to next treatment (rwTTNT), and real-world overall survival (rwOS), all assessed in months. Log rank test was used to compare Kaplan-Meier survival curves. Results: Of 1495 patients with >1 ctDNA alteration detected, a guideline-recommended biomarker was identified in 18% of patients. In patients with intrahepatic CCA (n=403), 11% had an IDH1 mutation, 9% an FGFR2 fusion, 1% MSI-H detected, 1% BRAF V600E mutation, <1% ERBB2 amplification and <1% RET fusion. Testing was performed prior to first-line therapy, after first-line therapy and after second-line therapy in 34%, 46% and 21% of patients respectively. Gemcitabine and cisplatin represented the most common first-line therapy (48%). FOLFOX (21%), gemcitabine and cisplatin (13%), and capecitabine (11%) were the most common second-line therapies. Among ivosidenib-naïve patients with an IDH1 mutation, 58 (20%) started therapy within 90 days of ctDNA test: 36% received ivosidenib, 57% received chemotherapy, 7% received other therapy. Patients with IDH1 mutations treated with ivosidenib (n=21) had numerically improved rwTTD and rwTTNT compared to those receiving chemotherapy (n=33) [rwTTD: 4.6 (95% CI:2.6-8.6) vs 2.8 (95% CI:2.0-6.3), p=0.1011; rwTTNT 11.0 (95% CI:5.7-NE) vs 5.2 (95% CI:3.3-NE); p=0.2559]. There was no difference in rwOS between patients receiving ivosidenib vs not. However, sample size was small. Conclusions: The rate of actionable molecular alterations detected via ctDNA is 18%, comparable to reports from tissue-based testing. Patients with aCCA are often tested before starting first or second LOT. Patients with ctDNA-detected IDH1 mutations treated with ivosidenib and had a trend toward improved rwTTD and rwTTNT, although it did not reach statistical significance. This data supports the clinical utility of liquid biopsy to identify aCCA patients who may benefit from targeted therapy.