Successful treatment with conversion surgery following chemoradiotherapy for unresectable invasive intraductal papillary mucinous neoplasm

Recent advances in chemotherapy and chemoradiotherapy (CRT) have enabled the use of conversion surgery in selected patients with initially unresectable pancreatic duct adenocarcinoma after a favorable response to preoperative treatment. However, conversion surgery for invasive intraductal papillary mucinous neoplasm (IPMN) has not been reported. A 63-year-old man was referred to our hospital for invasive IPMN treatment. Computed tomography revealed a multilocular tumor of 7.2 × 5.8 cm in diameter, which surrounded approximately 180° of the superior mesenteric artery and totally occluded the superior mesenteric vein (SMV). He was diagnosed with unresectable invasive IPMN. CRT was performed using four cycles of S-1 (100 mg/day) based on body surface area for 14 days every 3 weeks plus gemcitabine 1,000 mg/m2 on days 8 and 15 with concurrent radiotherapy (50.4 Gy in 28 fractions). Response to chemotherapy revealed partial response according to the Response Evaluation Criteria in Solid Tumors; subsequently, subtotal stomach-preserving pancreaticoduodenectomy with SMV resection was performed. The postoperative course was uneventful. Four courses of adjuvant chemotherapy with TS-1 100 mg / day were administered postoperatively. At 5 years and 9 months after initiating treatment, the patient was alive without recurrence.