[A Case of Conversion Surgery for an Initially Locally Advanced Unresectable Pancreatic Cancer after S-1 Chemotherapy].

We report a case of conversion surgery for a locally advanced unresectable(UR-LA)pancreatic cancer that was radically resected after S-1 therapy. A 65-year-old man visited a referral physician because of fatigue and liver dysfunction. A CT scan revealed a mass in the pancreatic uncinate process that was suspected to be superior mesenteric artery(SMA)infiltration and was diagnosed as UR-LA pancreatic cancer. GEM nab-PTX therapy was initiated but was discontinued after 2 courses because of adverse events. The treatment was switched to S-1 monochemotherapy. After that, the tumor did not progress for around 1.5 years, and the patient was referred to our hospital for surgical treatment. As the contact between the tumor and the SMA was considered to be less than half-round, we made a diagnosis of borderline resectable(BR-A)pancreatic cancer. Subsequently, we performed a pancreaticoduodenectomy with partial resection of the portal vein and achieved R0 resection. The patient received adjuvant chemotherapy with S-1 and showed no signs of recurrence for 10 months after surgery.