[A case of adjuvant surgery for a patient with initially unresectable locally advanced pancreatic cancer (LAPC) with a favorable response to S-1 chemotherapy].

A 67-year-old man was admitted to our hospital with a complaint of epigastric discomfort. A 29-mm hypovascular tumor was detected in the head of the pancreas by abdominal computed tomography imaging. As the superior mesenteric artery (SMA) was also involved, we diagnosed the tumor as unresectable pancreatic cancer. With S-1 chemotherapy, a radiological partial response was seen. After 4 courses of chemotherapy, a subtotal-stomach-preserving-pancreatoduodenectomy with dissection of the nerve plexus surrounding the SMA was performed. Although the tissue surrounding the SMA was hard, invasion of the SMA was not detected. Microscopic investigation revealed a few moderately differentiated adenocarcinoma cells in the fibrous tissue and the nerve fibers of pancreas. No cancer cells were found at the edges of the surgical specimen. The patient underwent R0 resection and a pathological evaluation showed Grade III tumor according to the Evans classification. After surgery, S-1 was interrupted because of diarrhea and local recurrence appeared 4 months postoperatively. For improving the prognosis of patients with pancreatic cancers, surgical intervention is often performed in patients with initially unresectable pancreatic cancers who have "long-term" favorable responses to chemotherapy or chemoradiotherapy. However, because of the possibility of relatively good prognosis with nonsurgical treatment for such patients and also the demerits of surgical stress, it is important to carefully consider the adjuvant surgery option.