[A clinical study on optimization of dose distribution in 60Co RALS for carcinoma of the uterine cervix using X-ray CT images].

From 1983 to 1992, 248 patients with carcinoma of the uterine cervix were treated with intracavitary radiation therapy using the 60Co remotely controlled high dose rate afterloading system apace (RALS). Five-year survival rates were 92,8 +/- 7 % for Stage I, 72.4 +/- 5% for Stage II and 52.1 +/- 4% for Stage III. The relations among the sequelae in surrounding organs, local control rates and the calculated dose in the rectum, sigmoid colon, bladder and small intestine were evaluated using X-ray CT images. The patients were treated with intracavitary radiation of 6 Gy/fraction at point A. A total of 5 fractions were delivered once a week. The dose calculation was performed by, and dose distribution shown on, a system developed in our hospital with a personal computer. The average values of maximum dose at certain points of the walls of the rectum and sigmoid colon were similar to point A dose. The incidence of late sequelae increased significantly in the group receiving a maximum dose to the rectum and sigmoid colon higher than 8 space Gy/fraction. This report describes the program for automatic optimization of dose distribution by modifying the hot spot (higher than 8 space Gy/fraction) and the cold spot (lower than 6 space Gy/ fraction).