Radiat Med. 1998 May-Jun;16(3):195-200. Response of unresectable pancreatic cancer to intraoperative radiotherapy. Department of Radiology, Hirosaki University School of Medicine, Aomori, Japan. Eight patients with unresectable pancreatic cancer were treated by intraoperative radiotherapy (IORT) with electron beams, and the tumor responses were followed using serial CT scans. In five cases, external beam irradiation with 10 MV X-rays was added. While there was no evident change after 2-3 weeks, 6-8 weeks after IORT partial responses were noted in all five examined cases. Furthermore, 12-16 weeks after IORT, three out of five examined patients showed good tumor response with more than 75% regression. Mean survival time was 8.0 +/- 2.7 months. Two patients who lived longer than 1.5 years had shown excellent tumor responses. Serial CT scans in the early period following IORT allowed accurate estimation of the tumor response, which might predict some long- surviving cases.