Comparison of Volumetric Modulated Arc Therapy and Intensity Modulated Radiotherapy with Brachytherapy for Carcinoma Cervix Boost

Abstract

Introduction: It is challenging to deliver brachytherapy for patients who refuse minor surgical insertion of applicators. As external beam radiation therapy(EBRT) can be delivered more precisely using advanced radiotherapy techniques, this study compares the dosimetric differences between intensity-modulated radiation therapy(IMRT), volumetric-modulated arc therapy(VMAT), and intracavitary brachytherapy (ICBT) for cervix boost. Material and Methods: Thirty patients with cervix cancer treated with 3-dimensional conformal radiation therapy (3DCRT) followed by ICBT were considered retrospectively for this study. IMRT and VMAT plans were generated for high-risk clinical target volume (HR-CTV). The dose prescription for VMAT and IMRT plans were the same as the ICBT, between 6 to 7.5 Gy per fraction. Target coverage (TC), organ at risk(OAR) doses, conformity index(CI), homogeneity index(HI), BED(biologically effective dose), and EQD2(2Gy equivalent dose) were calculated. IMRT and VMAT were compared with ICBT. Results: The EBRT plans in comparison to ICBT gave exceptional target coverage greater than 95%. Mean dose and D2cc to bladder and rectum in the EBRT plans were higher than ICBT. Dose to bladder, rectum and femur were high in the IMRT plans. Bowel bag dose in ICBT was higher compared to EBRT. Target conformity was superior for ICBT compared EBRT, however homogeneity was better for the EBRT plans. EQD2 values for bladder and rectum for all three plans were well within accepted tolerances. Conclusion: The current study dosimetrically suggests that in the absence of a Brachytherapy unit or if patients are unwilling to brachytherapy, EBRT can be opted for, with VMAT being the more suitable choice of treatment.