HER2-positive advanced biliary tract cancer responds to second-line pyrotinib therapy: a case report

Biliary tract cancers are solid tumors with poor prognosis and over 70% of patients present in advanced stages. The efficacy of second-line treatment for patients who progressed on GC chemotherapy is limited. Median OS of these patients is less than 1 year with palliative treatment. Despite the success of anti-HER2 therapy in HER2-positive breast cancer, the targeted therapy of HER2 mutations in BTCs is still being explored. This case report is the first report suggesting a 15-month PFS and partial response of pyrotinib in HER2-positive BTC. We report a 64-year-old female with HER2-positive biliary tract cancer. She was diagnosed with AJCC clinical stage IV (cT3N1M1) intrahepatic biliary tract cancer and got PD after 3 cycles of systemic chemotherapy of gemcitabine plus cisplatin. Due to the HER2-positive signature, pyrotinib (400 mg daily in 21-day cycles), an oral irreversible pan-ErbB TKI was prescribed in September 2021, with her informed consent. The tumor shrank significantly after this treatment and imaging assessments conducted on 24 September 2022 showed PR. Until the writing of the case draft, the patient had achieved 15 months of PFS. The present case suggests that Pyrotinib might be a potential effective treatment for HER2-positive advanced BTC.