Feasibility of HER2-Targeted Therapy in Advanced Biliary Tract Cancer: A Prospective Pilot Study of Trastuzumab Biosimilar in Combination with Gemcitabine Plus Cisplatin

SIMPLE SUMMARY: Unresectable or metastatic biliary tract cancer (BTC) has a poor prognosis with the standard gemcitabine and cisplatin (GemCis) regimen. Given the considerable incidence of HER2-overexpressing tumours (e.g., >10% of gallbladder cancer), HER2 is a potential therapeutic target in advanced BTC. In this prospective study, 7 out of 41 (17.1%) patients had HER2-positive tumours, and 4 patients (9.8%) subsequently proceeded to receive HER2-targeted therapy. The combination of trastuzumab-pkrb, an anti-HER2 monoclonal antibody, and GemCis resulted in high overall response (50%) and disease control (100%) rates in HER2-positive advanced BTC patients without new safety issues. This is the first prospective study that suggested the feasibility of HER2-targeted combination chemotherapy in advanced BTC patients. Future prospective randomised trials using HER2-targeted agents are warranted. ABSTRACT: The prognosis of advanced biliary tract cancer (BTC) is poor with the standard gemcitabine and cisplatin (GemCis) regimen. Given that the rates of human epidermal growth factor receptor 2 (HER2) positivity in BTC reaches around 15%, HER2-targeted therapy needs further investigation. This study aims to evaluate the preliminary efficacy/safety of first-line trastuzumab-pkrb plus GemCis in patients with advanced BTC. Patients with unresectable/metastatic HER2-positive BTC received trastuzumab-pkrb (on day 1 of each cycle, 8 mg/kg for the first cycle and 6 mg/kg for subsequent cycles), gemcitabine (1000 mg/m(2) on day 1 and 8) and cisplatin (25 mg/m(2) on day 1 and 8) every 3 weeks. Of the 41 patients screened, 7 had HER2-positive tumours and 4 were enrolled. The median age was 72.5 years (one male). Primary tumour locations included extrahepatic (N = 2) and intrahepatic (N = 1) bile ducts, and gallbladder (N = 1). Best overall response was a partial response in two patients and stable disease in two patients. Median progression-free survival (PFS) was 6.1 months and median overall survival (OS) was not reached. The most common grade 3 adverse event was neutropenia (75%), but febrile neutropenia did not occur. No patient discontinued treatment due to adverse events. Trastuzumab-pkrb with GemCis showed promising preliminary feasibility in patients with HER2-positive advanced BTC.