Dosimetric Impact of Planning Techniques on EQD2 and Management of OARs Doses in Intracavitary Brachytherapy in Cervical Cancer

Abstract

OBJECTIVE The purpose was to observe the impact of Equivalent dose of 2Gy (EQD2) for different planning technique combined with intracavitary brachytherapy (ICBT) for cervix patients and to manage the organ at risks (OARs) doses in external beam radiation therapy (EBRT) and brachytherapy to respect the EQD2 tolerances. METHODS Retrospectively, 15 patients of federation of gynecologists and obstetricians Stage IB-IVA, received a dose of 45Gy in 25 fractions with a simultaneous integrated boost of 55Gy in 25 fractions to the nodes with EBRT followed by three applications of ICBT of a dose of 8Gy, were selected. Intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) plans were created for each patient with a single iso-center with 6MV photon energy. EQD2 of D2cc, D1cc, and D0.1cc of bladder and rectum were compared for IMRT followed by ICBT and VMAT followed by ICBT. RESULTS The IMRT and VMAT plans were comparable in terms of target coverage and OARs sparing. The conformity index and homogeneity index were comparable for both IMRT and VMAT with p=0.007. In VMAT and ICBT plan the EQD2 of D2cc, D1cc, and D0.1cc for bladder were reduced 0.66%, 0.41%, and 0.41%, respectively, from IMRT and ICBT plan. CONCLUSION We recommend following VMAT and ICBT over IMRT and ICBT due to advantages of VMAT over IMRT and try to keep doses of OARs as low as possible in both EBRT and BT separately.