[A Case of Duodenal Cancer with a History of Metachronous Multiple Colorectal Cancer Resections Achieving Endoscopic Complete Response following Pembrolizumab Treatment].

Abstract

A male in his 80s with a history of multiple colorectal cancer resections underwent an upper gastrointestinal endoscopy for anemia investigation, which revealed a non-ampullary duodenal carcinoma. Due to insufficient surgical tolerance for pancreaticoduodenectomy, pharmacotherapy was considered. With informed consent, an MSI test was conducted, showing MSI-high, leading to the initiation of pembrolizumab treatment. Four months after treatment began, the tumor reduced on upper gastrointestinal endoscopy and became difficult to identify after 1 year. Meanwhile, a CT scan performed during the tumor reduction process revealed a 15 mm nodule on the dorsal side of the pancreatic uncinate process, accompanied by a gradual increase in CA19-9 levels. At the time of complete response of the primary lesion, CA19-9 levels were abnormally high at 1,192 U/mL, and a CT scan showed a slight increase of the nodule to approximately 17 mm, with FDG-PET indicating an SUVmax of 4.17. The patient did not wish to undergo invasive procedures such as a needle biopsy. Therefore, radiation therapy(IMRT-VMAT 60 Gy/30 Fr)was administered to control the lesion, resulting in a significant reduction in CA19-9 levels and the avoidance of decreased ADL in this elderly patient due to treatment changes.