Development of a vaginal immobilization device: A Treatment-planning Study of Carbon-ion Radiotherapy and Intensity-modulated Radiation Therapy for Uterine Cervical Cancer

Abstract

Aim: We developed a vaginal immobilization device for external radiotherapy in gynaecological malignancies and evaluated its bowel dose-reduction effect during carbon-ion radiotherapy (CIRT) and intensity-modulated radiation therapy (IMRT) in patients with cervical cancer. Patients and Methods: Computed tomographic images obtained with and without the device in seven patients with cervical cancer were assessed. Treatment plans for CIRT and IMRT were generated, and dose–volume parameters (V20, V25, V35, and D2cc) of the rectum, sigmoidal colon, and bladder were evaluated. Results: The mean±standard deviation of the rectal volume in CIRT for V35 with and without the device were 2.1±2.1 and 13.6±4.4 ml, respectively, and those in IMRT were 2.0±2.2 and 13.7±3.8 ml, respectively; these values were significantly lower in CIRT and IMRT using this device. Conclusion: Using our novel vaginal immobilization device, high rectal doses were largely reduced in CIRT and IMRT.