Gastric Cancer Treated with 5-Fluorouracil Following Discontinuation of Adjuvant S1 Plus Docetaxel and Capecitabine Plus Oxaliplatin Due to Drug-Induced Acute Pancreatitis: A Case Report

Introduction: Drug-induced acute pancreatitis (DIAP) is a rare cause of acute pancreatitis, accounting for approximately 3–5% of cases, and reports of chemotherapy-induced pancreatitis remain limited. Case presentation: Herein, we present the case of a 68-year-old man who developed DIAP during adjuvant chemotherapy with S-1 plus docetaxel and later with capecitabine plus oxaliplatin following surgery for gastric cancer. A drug-induced lymphocyte stimulation test (DLST) was conducted to identify the suspected agents, yielding positive results for S-1 and capecitabine, whereas docetaxel and oxaliplatin were negative. Unexpectedly, the DLST result for 5-fluorouracil was negative. Based on these findings, adjuvant chemotherapy was switched to 5-fluorouracil plus leucovorin, which was successfully continued without recurrence of pancreatitis. Shortly thereafter, the patient was diagnosed with recurrent gastric cancer. However, palliative chemotherapy with 5-fluorouracil–based regimen was safely continued. Conclusion: Although DIAP can be fatal, the DLST may help identify the suspected causative drug and contribute to decision-making in important clinical situations such as cancer treatment.