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: 60 Co and 192 Ir

Iridium-192 ( Ir) has been a widely accepted radioisotope for high-dose-rate (HDR) brachytherapy. Recently, Cobalt-60 ( Co) radioisotope with a longer half-life (5.26 years) has been gaining popularity due to economic and logistical reasons as compared with the traditional Ir. 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 Ir HDR source. For each patient plan, one additional set of plan was created using Co source in place of Ir 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 Co plan than that in Ir plan. For OARs, the mean ID to the rectum was significantly higher by 2.60% in Co plan as compared to Ir plan, whereas for bladder and sigmoid colon, it was lower in Co plan than that in Ir 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 Co plan than that of Ir plan. The results of our study concluded that Ir HDR radioisotope should be preferred for intracavitary brachytherapy due to its ideal physical characteristics for better clinical outcomes.