Japan gastric trials in intraoperative radiation therapy.

Based upon our clinical results indications of intraoperative radiotherapy (IORT) for gastric cancer were summarized as follows: (a) The primary tumor must be surgically removed. (b) There must be no metastases to the liver or peritoneum. (c) Serosal invasion must be limited to the posterior wall of the stomach. IORT is not adaptable to patients in whom there is direct invasion of the peritoneum beyond the anterior wall because of the ease of peritoneal dissemination. (d) All unresectable lesions must be encompassed by a single radiation field. (e) No significant difference between cumulative survival of patients with Stage I gastric cancer who were treated by IORT or surgery alone was found. Therefore IORT may be of no benefit to the prognosis of patients with Stage I gastric cancer. As for the IORT dose, it is recommended that for clinically undetectable lesions a single dose of 28 Gy be delivered. For macroscopic remnants 30-35 Gy should be delivered depending upon the residual tumor size. The electron energy is selected so that the entire lesion is included by the 90% isodose line. When IORT is applied to a curative operation, the radiation field is positioned toward the lymph node groups around the celiac axis, which are hard to eliminate by a surgical procedure.