Toxicities and dose–volume histogram parameters of MRI-based brachytherapy for cervical cancer

Abstract Purpose To analyze the toxicities and dose–volume histogram parameters of external-beam and magnetic resonance imaging–based intracavitary brachytherapy in cervical cancer patients. Methods and Materials Acute and late toxicities were assessed in 135 patients divided into four groups: group 1, grade 0; group 2, grades 1–4; group 3, grades 0–1; and group 4, grades 2–4. The doses at the International Commission on Radiation Units and Measurements (DICRU ) and minimum doses to the most exposed 0.1, 1, 2, and 5 cc (D0.1cc , D1cc , D2cc , and D5cc ) of normal organs were calculated as equivalent doses in 2 Gy (α/β = 3). Results The median follow-up was 35.2 months. For rectum, DICRU , D0.1cc , D1cc , and D2cc were significantly different between groups 1 and 2 and DICRU , D0.1cc , and D1cc between groups 3 and 4. For bladder, D0.1cc , D1cc , and D2cc were significantly different between groups 1 and 2 and DICRU , D1cc , D2cc , and D5cc between groups 3 and 4. Grade 2–4 bladder toxicity occurred in fewer patients with D2cc ≤ 95 Gy than those with D2cc > 95 Gy (7% vs. 22%, p = 0.014). Conclusions DICRU , D0.1cc , D1cc , and D2cc are relevant for predicting late rectal toxicities. The patients with bladder D2cc > 95 Gy are required to be in close observation for severe late toxicities.