[Injuries of the sigmoid colon following radiation therapy of carcinoma of the uterine cervix--a method of estimating the radiation dose to the sigmoid colon].

Grade 2 or 3 injuries of the sigmoid colon were observed in 4 out of 42 patients with carcinoma of the uterine cervix who were treated by radiation therapy. The irradiation was planned as the combination of the external irradiation (whole pelvic 30 Gy and 20 Gy with central shielding by 25 fractions, 5 weeks) and the intracavitary irradiation (RALS, 19 Gy at point A by 3 fractions). To analyze the causes of the radiation sigmoiditis, we have investigated the following factors: age, dose at point A, dose at point C, grade of tandem dislocation, uterine angle, obesity score, evidence of previous surgery to the pelvic cavity and hypertension. The dose at point C and the grade of tandem dislocation were determined from the confirming X-Ps at RALS therapy and external irradiation. The superimposition of these films was performed with corrections for the angle between the projection direction of the X-Ps and the vertical magnification factor of the central shielding area. Point C was defined as a point 2 cm anterior to the intersection of the tandem axis and a curvilinear line 1 cm outside from the margin of central shield on the X-Ps. Grades of tandem disclocation were decided as the number of tandem tips which were outside of the central shielding area on X-Ps. As the results, the doses at point C showed very high statistical significance (p less than 0.001) with the evidence of radiation sigmoiditis. All the cases with radiation sigmoiditis were received over 1290cGy at point C. Age had also some significance (p less than 0.05) with radiation sigmoiditis.(ABSTRACT TRUNCATED AT 250 WORDS)