APPLICATION OF RADIATION EFFECT MODELS IN COMBINED EXTERNAL AND INTRACAVITARY RADIOTHERAPY OF CARCINOMA OF THE UTERINE CERVIX

A retrospective analysis of 291 patients with cancer of the uterine cervix treated with a combination of external and intracavitary radiotherapy was carried out. Patients were treated with an external radiotherapy dose of 45 Gy in 20 fractions, 5 fractions per week, or 42 Gy in 14 fractions, 3 fractions per week. For brachytherapy the total dose was 24 to 32 Gy at a dose rate of 1.4 to 2.2 Gy per hour. Treatment results in terms of survival, local disease-free survival and complication rates were compared with cumulative radiation effect (CRE) and extrapolated response dose (ERD) values for point A (CRE(TA) and ERD(TA) respectively) and for rectum (CRE(Tr) and ERD(Tr) respectively). CRE(TA) and ERD(TA) values did not significantly correlate with local disease-free and survival rates. Correlations of CRE(TA) and ERD(TA) with overall complication rate and with rectal complication rate (p-value < 0.025) were good. No significant correlation was observed between CRE(Tr) or ERD(Tr) and overall complication rate and rectal complication rate. In order to limit grades II and III rectal complications to acceptable level, in combined external and intracavitary treatment, CRE(TA) and ERD(TA) values of less than 2 500 and 93 respectively are suggested.