The dose time relationship in the radiotherapy of carcinoma of the cervix--application of CRE formalism.

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 either treated with 45 Gy in 20 fractions by five fractions per week or with 42 Gy in 14 fractions by three fractions per week or with 42 Gy in 14 fractions by three fraction per week schedule by external radiotherapy. For brachytherapy the total dose was 24 to 32 Gy at a dose rate of 1.4 to 2.2 Gy per hour. Complication were correlated with total CRE values for point A (CRE TA) and for rectum CRE TR. Correlations of CRE TA with overall complication rate (p value < 0.05) and rectal complication rate (p value < 0.01) were excellent. Lack of correlation was observed between CRETR and overall complication rate (p value > 0.1) as well as rectal complication rate (p value > 0.1). In order to limit Grade II and III rectal and bladder complications to acceptable level, in combined external and intracavitary treatments, CRETA value of less than 2500 reu is suggested.