[Preoperative radiotherapy in rectal carcinoma. 2. The effect of irradiation on lymph node involvement]

A total of 38 cases of advanced rectal cancer (non-radiation group; 25 cases, radiation group; 13 cases) was studied in order to clarify the effect of preoperative radiation therapy (42.6 Gy) on lymph node metastases in rectal carcinoma. In all cases, microcarbon was submucosally injected into the rectal wall the day before operation in order to increase the number of removable lymph nodes from resected specimens as many as possible. By this method, the number of lymph nodes detected per specimen increased from 40 to 60. The incidence of lymph node metastases was 38.5% in radiation group and 64.0% in non-radiation group. The mean number of lymph nodes with metastases was 8.6 in non-radiation group, however, 2.8 in radiation group. With regard to the relationship between size and number of positive lymph nodes, especially in small lymph nodes measuring less than 3 mm, the incidence of metastases was 6.4% in non-radiation group, whereas 0% in radiation group. As a result, it was evident that preoperative radiation therapy in rectal cancer would reduce the number of positive lymph nodes significantly and the effect of radiation was prominent in small lymph nodes.