Impact of dosimetric and clinical parameters on clinical side effects in cervix cancer patients treated with 3D pulse-dose-rate intracavitary brachytherapy

Background and purpose: To assess the association between dosimetric/clinical parameters and gastrointestinal/urinary grade 2–4 side effects in cervix cancer patients treated with 3D pulse dose rate brachytherapy. Materials and methods: Three hundred and fifty-two patients received brachytherapy associated with external-beam radiotherapy (EBRT) for 266 of them; 236 patients underwent surgery. The doses for the most exposed 2, and 0.1 cm3 (D2cc and D0.1cc) volumes of the rectum and bladder as well as bladder ICRU point dose (DICRU) were converted into isoeffective doses in 2-Gy fractions. The clinical parameters analyzed were: age, smoking habits, arteritis, diabetes, previous pelvic surgery, FIGO stage, nodal status, pathology, pelvic surgery, EBRT and chemotherapy. Side effects were prospectively assessed using the CTCAEv3.0. Cutoff dose levels were defined separately for patients treated with EBRT and brachytherapy (Group 1) and with preoperative brachytherapy (Group 2). Results: The median follow-up was 23.4 months. In Group 1 a significant predictive value of rectum D0.1cc and D2cc, bladder D0.1cc and DICRU for gastrointestinal and urinary toxicity was found using as cutoff 83, 68, 109 and 68 Gyα/β3. In Group 2 a significant predictive value of bladder D0.1cc, D2cc and DICRU for urinary toxicity was found using as cutoff 141, 91 and 67 Gyα/β3, but not for the rectum D0.1cc and D2cc; smoking had a significant predictive value on urinary toxicity. Conclusions: For patients treated with brachytherapy and EBRT, rectum D0.1cc and D2cc and bladder D0.1cc and DICRU had a predictive value for toxicity. For patients treated with preoperative brachytherapy, bladder D0.1cc, D2cc and DICRU and smoking had a predictive value for urinary toxicity.