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

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 (D _ICRU ) and minimum doses to the most exposed 0.1, 1, 2, and 5 cc (D _0.1cc , D _1cc , D _2cc , and D _5cc ) 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, D _ICRU , D _0.1cc , D _1cc , and D _2cc were significantly different between groups 1 and 2 and D _ICRU , D _0.1cc , and D _1cc between groups 3 and 4. For bladder, D _0.1cc , D _1cc , and D _2cc were significantly different between groups 1 and 2 and D _ICRU , D _1cc , D _2cc , and D _5cc between groups 3 and 4. Grade 2-4 bladder toxicity occurred in fewer patients with D _2cc  ≤ 95 Gy than those with D _2cc  > 95 Gy (7% vs. 22%, p = 0.014).
Conclusions: D _ICRU , D _0.1cc , D _1cc , and D _2cc are relevant for predicting late rectal toxicities. The patients with bladder D _2cc  > 95 Gy are required to be in close observation for severe late toxicities.
(Copyright © 2016 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.)