A Dosimetric Study of Optimised and Non-Optimised Plans in Intracavitary Brachytherapy (ICBT) Using International Commission on Radiation Units and Measurement (ICRU) 89

The study aimed to assess the effectiveness of the dosimetric parameters of organs-at-risks (OARs) and target coverage in optimized plans compared to non-optimised plans normalized at point A.
This retrospective study examined 21 patients with cervical cancer in stages II and III, who had undergone a high dose rate (HDR) ICBT following external beam radiotherapy(EBRT).In this study, two treatment plans were created for each case using computed tomography (CT) images. Normalization at point A was performed in the non-optimised plans, and 90% of the high-risk clinical target volume (HR-CTV) was to receive the prescribed dose in the optimised plans. Dose-volume histograms (DVH) were used to compare D5cc, D2cc, D1cc, and D0.1cc (minimum doses received by the most irradiated volumes of5cc, 2cc, 1cc and 0.1cc, respectively) for OARs as well as the D90%, D50%, D98%, D100%, and D95% coverage of HR-CTV between the non-optimised and optimised plans. Statistical analysis was performed using Wilcoxon signed rank test.
The HR-CTV coverage improved in 80% of the patients. In the optimised plans, the rectum and bladder doses decreased by 8.75% and 9.85%, as compared to the non-optimised plans normalized at point A, respectively. In the sigmoid and bowel cases, there were dose drops by 8.95% and 9.75%, in the optimised plans, respectively.
Target coverage and OAR sparing were more satisfactory in the optimised plans than the non-optimised plans normalized at point A.