Impact of different treatment plans on EQD for intracavitary brachytherapy of cervical cancer.

Background: Cancer is one of the leading causes of death worldwide. According to GLOBOCAN estimates, there were 341,831 deaths from cervical cancer in 185 countries in 2020. The aim of this study was to compare equieffective dose (EQD) at 2 Gy per fraction by using dose volume histograms (DVHs) derived from external beam radiotherapy (EBRT) and high-dose rate brachytherapy (HDR-BRT) treatment plans used in cervical cancer radiotherapy.

Methods: Fifteen patients with stage IIB-IIIB cervical cancer were included in this retrospective study. Treatment with three-dimensional conformal radiotherapy (3D-CRT) or intensity-modulated radiotherapy (IMRT) was planned for all patients in 28 fractions, with a total of 50.4 Gy to be delivered to the whole pelvic region. After EBRT, manual optimization (MO) or inverse optimization (IO) HDR-BRT plans were created in 4 fractions with a total of 28 Gy. The plans obtained were grouped as IMRT + IO, IMRT + MO, 3DCRT + IO, and 3DCRT + MO by calculating EQDs among these plans. D, D, and D values were compared in all plans for CTV total EQD. In addition, EQD values ​for critical organs at risk (OARs) such as rectum, bladder, small intestine, and sigmoid were compared in all plans for volumes of 2 cm, 1 cm, and 0.1 cm, respectively.

Results: There was no significant difference between the treatment groups in terms of CTV D and CTV D values; However, CTV D (p = 0.000) and CTVHR D98 (p = 0.000) values ​were found to be better in IMRT + IO technique. The IMRT + IO technique provided better protection for 2 cm, 1 cm, and 0.1 cm volumes of OARs compared to other techniques.

Conclusions: Considering all parameters such as CTV, CTV, rectum, bladder, small intestine, and sigmoid, combination of IMRT + IO treatment option was found to be significantly superior in total EQD2 calculations compared to other plans.