Comparison of Rectal and Bladder ICRU Point Doses to the GEC-ESTRO Volumetric Doses in CT-Guided Intracavitary Brachytherapy in a Private Philippine Institution

Abstract

Cervical cancer is the second most common malignancy and is the most common cause of cancer-related mortality among Filipino women. There are 22.5 cases per 100,000 women and an overall 5-year survival rate of about 44%. Brachytherapy remains to be an essential part in the management of cervical cancer. In the Philippine setting, the planning system traditionally used has been by x-ray. In the latter part of 2015, our institution has begun to make a transition into 3D brachytherapy planning with the use of a CT scan to define the clinical target volume.

This study compares the rectal and bladder ICRU point doses to the GEC-ESTRO volumetric doses in the CT-guided intracavitary brachytherapy procedures performed in our institution.
The treatment records of patients with cervical cancer treated with HDR brachytherapy from December 2015 to April 2016 were reviewed retrospectively. The rectum and the bladder were contoured on the CT data sets obtained at the time of the brachytherapy simulations. The D2cc was derived for each treatment. The volumetric doses were then compared for the ICRU point doses for the rectum and bladder.
The mean EQD2 dose to the rectum was 65.75 ± 7.70 Gy at DICRU, and 67.94 ± 6.52 at D2cc. The mean EQD2 dose to the bladder was 71.16 ± 13.98 Gy at DICRU and 74.89 ± 12.68 Gy at D2cc.
This study shows a Pearson’s correlation coefficient of >0.6 for ICRU and volumetric rectal and bladder doses, revealing a good to intermediate correlation between the two parameters.