Estimation and comparison of integral dose to target and organs at risk in three-dimensional computed tomography image-based treatment planning of carcinoma uterine cervix with two high-dose-rate brachytherapy sources: 60Co and 192Ir.

Abstract

Iridium-192 (192Ir) has been a widely accepted radioisotope for high-dose-rate (HDR) brachytherapy. Recently, Cobalt-60 (60Co) radioisotope with a longer half-life (5.26 years) has been gaining popularity due to economic and logistical reasons as compared with the traditional 192Ir. This study aimed to evaluate and compare the integral dose (ID) to the target and organs at risk (OARs) with two HDR brachytherapy sources in brachytherapy treatment of carcinoma uterine cervix to find appropriate HDR radioisotopes for clinical benefit. This is a retrospective analysis of 52 computed tomography image-based brachytherapy plans of 52 patients who have received intracavitary treatment with 192Ir HDR source. For each patient plan, one additional set of plan was created using 60Co source in place of 192Ir source keeping the same dwell position, and again dose was optimized. The volume and mean dose for target, OARs, and volume structures of 400%, 200%, 150%, 100%, and 50% were recorded for the estimation and comparison of ID. The mean ID to high-risk clinical target volume was significantly higher by 5.84% in 60Co plan than that in 192Ir plan. For OARs, the mean ID to the rectum was significantly higher by 2.60% in 60Co plan as compared to 192Ir plan, whereas for bladder and sigmoid colon, it was lower in 60Co plan than that in 192Ir plan. The mean ID of central dose volume structures of 400%, 200%, 150%, 100%, and 50% was higher by 12.97%, 9.77%, 8.16%, 6.10%, and 3.22%, respectively, in 60Co plan than that of 192Ir plan. The results of our study concluded that 192Ir HDR radioisotope should be preferred for intracavitary brachytherapy due to its ideal physical characteristics for better clinical outcomes.