Dosimetric comparison between single-channel and six-channel vaginal cylinders with three-dimensional treatment planning in postoperative brachytherapy for endometrial carcinoma

Abstract

Objective To evaluate whether the three-dimensional (3D) CT-guided treatment planning for postoperative brachytherapy of endometrial carcinoma offers any advantage over the two-dimensional (2D) planning with single-channel and six-channel vaginal cylinders. Methods Ten patients with endometrial carcinoma treated with vaginal brachytherapy were included. Patients had CT scan with six-channel and single-channel vaginal cylinders. The clinical target volume (CTV) was defined by the upper 3 cm of vagina and submucous 5 mm in all directions. The dose prescribed was 5 Gy with six fractions. Each patient with various cylinders underwent 2D and 3D planning. The doses of CTV and organ at risk (OAR)were compared between 2D and 3D treatment planning between two cylinders. Results Both 2D and 3D plans for two cylinders showed excellent dose coverage to the CTV. Compared with 2D plan, 3D plan with single-channel vaginal cylinder significantly decreased the doses of 0.1, 1.0, and 2.0 cm3 to the rectum by 18.2%, 12.4%, and 10.7%. Similarly, 3D plans with six-channel vaginal cylinder significantly decreased the doses of 0.1, 1.0, 2.0 cm3, and Dmean to the rectum by 36.6%, 24.8%, 20.4%, and 6.1 %. In addition, it reduced the Dmean to the bladder and urethra. Compared with 3D plan for single-channel vaginal cylinder, 3D plan for six-channel vaginal cylinder significantly decreased the doses of the rectum, bladder and small intestine. Conclusions Three - dimensional CT - guided treatment planning, especially 3 D plan for six-channel vaginal cylinder, for postoperative brachytherapy of endometrial carcinoma decreased the doses to critical organs without compromising coverage of CTV with various cylinders. Key words: Endometrial carcinoma; Brachytherapy; Vaginal cylinder; CT-guided three-dimensional treatment planning