Longitudinal liquid biopsy and matched radiomic analysis indicated resistance mechanisms of patients with biliary tract cancer undergoing systemic treatment.

Abstract Background and aims: Data on the evolution of molecular alterations during first-line systemic anti-cancer treatment (SACT) are lacking for biliary tract cancers. Liquid biopsy and radiomics are non-invasive tools that could provide insights. Methods: Plasma samples collected at baseline (N=39) and progressive disease (PD, N=30) were subjected to NGS panel covering SNV and CNV [Avenio ctDNA-Expanded-kit]. CT scans were reviewed for total tumor burden (TTB) analysis and for an exploratory radiomic analysis. Results: cfDNA concentration correlated with TTB (p=0.0003). Intrahepatic cholangiocarcinomas (iCCA) had larger TTB (p=0.034) and higher number of alterations (p=0.02). cfDNA concentration or median dominant VAF did not correlate with outcomes. Baseline MET SNVs (p=0.07) and ERBB2 CNVs (p=0.03) were associated with shorter time to progression (TTP). iCCA frequently displayed a heterogeneous molecular response to SACT. Patients with increasing CNV score for EGFR [TTP: 4.1 vs 9.5 months, p=0.003; overall survival (OS): 10.1 vs 21.6 months, p=0.02] and MET [TTP: 4.2 vs 10.1 months, p=0.01; OS: 9.5 vs 20.2 months, p=0.06] had worse outcomes than those with decreasing score during SACT. Cases with PD driven by EGFR and MET were associated with selected baseline radiomic features: NGTDM Coarseness (p=0.041), GLSZM Zone Size Entropy (p=0.028) for EGFR; GLRLM Short Run Emphasis (p=0.034), GLRLM Run Length Variance (p=0.017), GLRLM Run Entropy (p=0.028), GLSZM Large Zone Emphasis (p=0.019) for MET. Conclusion: Liquid biopsy identified potential primary (MET SNVs/ERBB2 CNVs) and secondary (EGFR/MET CNVs) resistance mechanisms to platinum-based SACT. Radiomics provided an early correlation with molecular evolution.