[en] An 80-year-old woman was referred to our hospital for further examination of a tumor in the pancreas head. Laboratory data demonstrated elevated CA19-9 serum levels. Ultrasonography and computed tomography showed a solid tumor measuring 2 cm in diameter in the pancreatic head that directly invaded the portal vein. According to these findings, the patient was diagnosed with unresectable locally advanced pancreatic cancer. She was treated by chemotherapy with S-1 at a dose of 100 mg/day that had to be stopped after 1 course because of anorexia. Combination therapy with S-1 (50 mg/day) and radiation (50.4 Gy) reduced tumor size. After chemo-radiotherapy, S-1 was continued at a dose of 50 mg/day; however, a peripheral blood examination revealed anemia. Results of a bone marrow aspiration showed myelodysplastic syndrome (MDS), and is likely that combination therapy might have been the cause of secondary MDS. (author)