A Case of Microsatellite Instability-high Intrahepatic Cholangiocarcinoma that Was Effectively Treated with Pembrolizumab Following Multiple Chemotherapy for Two years after Non-curative Resection

Abstract

The patient was a 70-year-old woman. In 20XX, left hepatic lobectomy, caudate lobectomy, and extrahepatic cholangectomy were performed, and she was pathologically diagnosed with intrahepatic cholangiocarcinoma with a positive margin, stage III (T4N0M0). We administered 4 courses of tegafur/gimeracil/oteracil (S-1). In 20XX+1, CT revealed multiple lung metastases. Gemcitabine and cisplatin therapy was administered 17 times. This was switched to gemcitabine and S-1 therapy; 20 courses were administered. The metastatic lung lesions tended to increase, and progressive disease was diagnosed. We then examined the surgical specimen and noticed high frequency microsatellite instability (MSI-H). We changed the treatment regimen to pembrolizumab in 20XX+3. CT after 4 courses of pembrolizumab revealed that the tumor had shrunk and a partial response was achieved. We propose that MSI testing be actively considered.