Histopathological and Roentonological Study on Effects of Preoperative Irradiation Therapy for Rectal Cancer

To improve survival rate and to decrease local recurrence after operation of advanced rectal cancer, preoperative irradiation therapy with total dose of 42.6 Gy. has been performed in our department. In this study, we examined relationship between the histological effects and the roentogenographic changes in cases of rectal cancer treated with preoperative irradiation therapy. In fourty-one patients barium enema examination was performed before and after irradiation therpy, and the reduction rate of tumor diameter was measured on roentogenogram. Cancer gland ratio (CGR) and fibrosis ratio (FR), which were defined as the ratio of cancer glands and fibrosis to the tumor on histological section respectively, were measured by image analizer system. Histologically, 19 patients showed minor response (non-effective group), and the remaining 22 patients showed moderate to marked effects (effective group) for the radiation therapy. As a result, the tumor reduction rate on barium enema was 18.7 % on the average of all patients. According to histolgical effects, the tumor reduction rate on barium enema was 15.6 % ±6.7 % in non-effective group, and 21.7 % ±8.4 % in effective group, respectively. The difference was stastically significant (p < 0.01). There was significant correlation between CGR and the tumor reduction rate on barium enema (p < 0.01). But FR has no correlation with the tumor reduction rate on barium enema. It is suggested that tumor reduction was due to the decrease of the cancer glands, and tumor reduction rate on barium enema was a good clinical parameter of radiation effects.