Feasibility study of toxicity outcomes using GEC-ESTRO contouring guidelines on CT based instead of MRI-based planning in locally advanced cervical cancer patients

Abstract

PurposeTo report late rectal and bladder toxicity outcomes of a CT-based image-guided brachytherapy (IGBT) technique for treatment of cervical cancer. Methods and MaterialsBetween 2008 and 2014, 95 women with International Federation of Gynecology and Obstetrics stage IB to IVA cervical carcinoma treated with definitive concurrent cisplatin-based chemotherapy and external beam radiation therapy 50.4 Gy in 28 fractions followed by planned prescription dose of 7 Gy × 4 fractions of high-dose-rate IGBT was retrospectively reviewed. At each implantation, all patients had a urinary catheter in situ and received bowel enema before undergoing planning CT simulation. A high-risk clinical target volume (HRCTV) as per GEC-ESTRO guidelines and the entire cervix, rectum, and bladder was contoured on the simulation CT according to Radiation Therapy Oncology Group Gynaecology Contouring Atlas. Reported doses to HRCTV and organs at risk were recorded. Toxicities were recorded using National Cancer Institute Common Terminology Criteria for Adverse Events version 3. ResultsThe median followup time was 29 months. The mean HRCTV equivalent dose in 2 Gy fractions (EQD2) of external beam radiation therapy combined with brachytherapy was 80 Gy (standard deviation [SD], 11), and the rectal doses to 2 cm3 (D2cc) EQD2 and bladder D2cc EQD2 were 74 Gy (SD, 6) and 79 Gy (SD, 15), respectively. Twenty-two patients (23%) had grade 2 proctitis and 10 patients (11%) had grade 3 proctitis. Four patients (4%) had grade 2 cystitis and two patients (2%) had grade 3 cystitis. No patients had ≥ grade 4 toxicity. ConclusionsDespite CT-based brachytherapy planning, reported organ at risk toxicity was still significant compared with reported MRI-based planning series. Coimplementation of interstitial IGBT using the European Study on MRI-guided Brachytherapy in Locally Advanced Cervical Cancer (EMBRACE) protocol or using intensity-modulated radiation therapy during the external beam phase treatment might help to limit these late toxicities.