ERBB2 Pathway in Biliary Tract Carcinoma: Clinical Implications of a Targetable Pathway

Background/Aims: Current chemotherapy regimens for cholangiocarcinoma (CCA) yield poor outcomes, with a median overall survival of <12 months. Recent data on the genomic landscape of CCAs have created opportunities for targeted therapy. Yet, data regarding its efficacy are scarce. We aimed to describe the genomic landscape of a CCA patient cohort using next-generation sequencing (NGS), focusing on the ERBB/EFGR pathway and assessing response to anti-HER2 agents. Methods: Tissue samples of intrahepatic CCA (IHCC) and extrahepatic CCA (EHCC) underwent NGS for somatic aberrations. The clinical outcomes for patients treated with anti-HER2 agents were evaluated. Results: A total of 1,863 CCA cases (1,615 IHCCs and 248 EHCCs) underwent NGS, and they revealed a high prevalence of ERBB alterations (IHCC, 4.2%; EHCC, 9.7%). Among these, 23.8% of the IHCCs and 53.6% of the EHCCs had a point mutation in ERBB2, and 66.6% of the IHCCs and 41.2% of the EHCCs had ERBB copy number amplification. Three EHCC patients were diagnosed at our institute with ERBB/EGFR aberrations; 2 patients were treated with neratinib and 1 patient with a chemotherapy-trastuzumab combination. All 3 achieved disease stabilization and a clinical benefit. One patient underwent a liquid biopsy before and after 3 months of treatment, demonstrating disappearance of the ERBB2 clone and emergence of a Myc-mutated clone after treatment. Conclusions: The genomic landscape of CCAs may harbor targetable alterations, especially in the ERBB/EGFR pathway. These alterations may have clinical significance in everyday practice.