Experiences with Co-60 and Ir-192 high dose rate brachytherapy for carcinoma of the cervix

Abstract

A high-dose-rate (HDR) Co-60 brachytherapy was used in Maharaj-Nakorn-ChiangMai Hospital from 1986 to 2001. The five year survival rate of 1992 patients with carcinoma of the cervix treated with combined external beam radiation therapy (EBRT) and Co-60 HDR brachytherapy was reported in the year 2000. Ir-192 source was introduced in 2001 and the same treatment regimen was applied. We evaluated the incidence of late complication of 100 patients underwent the two HDR systems. The linear-quadratic (LQ) formula was used to calculate the biologically equivalent dose (BED) and reconverted to dose equivalent of fractionated irradiation at 2 Gy/fraction for simplicity. The a/b ratio of 10 Gy and 3 Gy were taken for tumor and late effect respectively and the late complication was scored according to RTOG late radiation morbidity scoring scheme. We found that for Co-60 HDR, the average BED10 and BED3 was 100.7 Gy and 94.5 Gy respectively corresponding to dose equivalent of 84.1 Gy and 56.7 Gy comparing to BED10 of 100.8 Gy and BED3 of 125.4 Gy for Ir-192 corresponding to dose equivalent of 84.1 Gy and 75.24 Gy, respectively. The complication was relatively higher in Ir-192 group but still comparable with other series. [J Radiat Res 44:370 (2003)]