This study aims to examine whether octreotide has an effect on inhibition of the exocrine secretion fo the pancreas, which might lower the rate of postoperative pancreatic fistula after pancreatoduodenectomy. Patients who will undergo pancreatoduodenectomy for periampullary tumors were enrolled. The patients were randomly assigned to intervention (use of octreotide) or placebo groups. Octreotide was injected subcutaneously every 8 hours for 7 days. Every patients will undergo pancreaticojejunostomy with external stent for remnant pancreas management. The pancreatic juice is drained through the external stent by negative pressure and amounted.