[A Case of Conversion Surgery for a Patient with Initially Unresectable Pancreatic Cancer with a Pathological Complete Response to S-1 Chemotherapy].

We present a case ofa 67-year-old woman with Stage IV pancreatic head cancer with invasion to the superior mesenteric vein and artery, and distant lymph node metastases. The patient received S-1 mono-chemotherapy. After 2 courses of chemotherapy, the tumor marker was decreased to the normal levels, and the tumor size was dramatically reduced with undetectable lymph node metastases on CT. As the disease status was maintained following chemotherapy, the patient underwent subtotal stomach preserving pancreaticoduodenectomy, 8 months after initiation of the chemotherapy. Histopathologically, no cancer cells were found in the main tumor and dissected lymph nodes. Final diagnosis was made with pathological complete response. The patient was alive without recurrence for 10 months after surgery.