Objectives Based on occult perforation CT images during brachytherapy in cervical cancer, to evaluate the dosimetric parameters between 3D plan and 2D plan for providing clinical reference.

Methods The patients with cervical cancer who received intracavitary (intrauterine tandem + vaginal colpostats) were retrospectively reviewed between January 2019 to December 2020 at Chongqing University Cancer Hospital. Based on Oncentra Brachytherapy planing system, same prescription 6Gy, design 3D and 2D plan on perforated CT images respectively. Target volume, conformity index (CI), conformal index (COIN) and organs-at-risk (OARs) D2cc were assessed in two plans.

Results A total of 817 patients were included in this study. Perforations were observed in 16 patients (1.96%). The volume of prescription dose curve in the 3D plan was significantly reduced 50.72±4.73 cm3 than 2D plan (P<0.05), but there was a similar volume of HR-CTV; the CI and COIN of 3D plan were promoted 0.41±0.01 and 0.35±0.78 than 2D plan (P<0.05), respectively; the dose received by OARs (bladder, rectum, sigmoid, small intestine) D2cc in 3D plan were significantly decerased [(241.97±86.64) cGy, (158.89±46.14) cGy, (100.20±31.64) cGy, (232.16±63.06) cGy] than 2D plan (P<0.05).

Conclusions Image-guidance brachytherapy of cervical cancer is helpful to detect hidden uterine perforation. When uterine perforation occurs, 3D plan can basically meet the clinical needs and is significantly better than 2D plan.