Comparison of ICRU Point Doses and Volumetric Doses to the Rectum during High Dose Rate Cobalt-60 Brachytherapy of Cervical Cancer
Brachytherapy is an important component of radiotherapy for cervical cancer treatment. High dose rate (HDR) intracavitary brachytherapy (ICBT) is one of the currently used techniques for cervical cancer treatment. The volume-based brachytherapy planning method recommended in the International Commission on Radiation Units and Measurements (ICRU) report No. 89 is believed to be more useful compared to the conventional point-based method recommended in ICRU report No. 38 in terms of organs at risks (OARs) dosimetry. However, more resources in terms of manpower and time are required to implement volume-based brachytherapy planning. This study aims to evaluate the point-based and volume-based methods for rectal dose estimation in HDR Cobalt-60 (Co-60) brachytherapy of cervical cancer. A total of 150 patient plans receiving full insertion HDR ICBT treatment in University of Malaya Medical Centre (UMMC) from 2017 to 2019 were retrospectively selected. The patients' data including rectal volume and rectal dose parameter calculated using both point-based and volume-based techniques were extracted from the brachytherapy treatment planning system. Data were compared and analysed for possible correlations between rectal point dose (ICRUr) and rectal volumetric doses. The ICRUr was shown to have no significant difference with the most exposed rectal volumes of 2 cm3 (D2cc) (p=0.960). The results of correlation analyses indicated strongest correlations between ICRUr versus D1cc and ICRUr versus D2cc with the correlation coefficients of 0.674 and 0.669 (p<0.05) respectively. The findings of the study fit with the existing theory that the volumetric doses can be explained well by the ICRU point dose with considerable significant correlations. The dose to ICRUr can be used to estimate volumetric dose to the rectum, specifically the D2cc for treating institutions that are practicing point-based planning for ICBT of cervical cancer.
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