Radiation sigmoiditis mimicking sigmoid colon cancer after radiation therapy for cervical cancer: the implications of three-dimensional image-based brachytherapy planning

External-beam radiation therapy with intracavitary high-dose-rate brachytherapy is the standard treatment modality for advanced cervical cancer; however, late gastrointestinal complications are a major concern after radiotherapy. While radiation proctitis is a well-known side effect and radiation oncologists make an effort to reduce it, the sigmoid colon is often neglected as an organ at risk. Herein, we report two cases of radiation sigmoiditis mimicking sigmoid colon cancer after external-beam radiation therapy with intracavitary high-dose-rate brachytherapy for uterine cervical cancer with dosimetric consideration.