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

Abstract

Background: 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. Aim: 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. Materials and Methods: 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. Results: 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. Conclusion: 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.

High dose rate 192Ir versus high dose rate 60Co brachytherapy: an overview of systematic reviews of clinical responses of gynecological cancers from 1984 to 2020

“…Conclusions. The use of HDR 60 Co brachytherapy has the capacity to produce overall survival rate and disease control in patients with carcinoma of the gynaecology comparable to that reported for HDR 192 Ir brachytherapy. Currently, the toxicity and damage of the normal tissues and radiation-related second cancers are of a similar incidence to that of standard HDR 192 Ir brachytherapy.…”

“…Owing to this problem, HDR brachytherapy was developed but did not receive much attention until the late 1980s, for there was much concern about damage to healthy tissues that could lead to an increase in late complications. Consequently, studies concerning biological equivalence dose (BED) of HDR 60 Co to LDR were examined by many researchers. It was found that if the scheduled system for HDR is converted from single fraction treatment to a fractional one, and the time of each fraction is reduced, the damage to healthy tissues is minimized [11,12].…”

“…Many novel technologies have been introduced into routine clinical practice. For example, manufacturing several gamma emitting isotopes, especially 137 Cs, 60 Co and 192 Ir sources and miniaturized high activity (dose rate>12 Gy/h) 192 Ir and 60 Co sources. In fact, the small size of these miniaturized sources facilitates production of small and flexible catheters that makes interstitial treatment to be feasible.…”

“…However, for many developing countries, HDR 192 Ir sources are not easily accessible and occasionally, by the time the customs paperwork and source shipment clearance are completed, a large proportion of useful activity can decay away. Therefore, HDR 60 Co brachytherapy sources (5.27 yr half-life) have been introduced to overcome some of these difficulties' [14]. It could therefore be inferred that using HDR 60 Co source for treating gynaecological lesions in developing countries is the only available option, because it is cost-effective and requires less frequency of source replacement.…”

Dosimetric comparison of integral dose for different techniques of craniospinal irradiation

“…The ID calculation is based on mean organ dose, mean organ density and organ volume. 24 It is defined by: where D − is the mean organ dose, V is the organ volume and ρ − is the mean organ density.…”