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

To analyze the toxicities and dose-volume histogram parameters of external-beam and magnetic resonance imaging-based intracavitary brachytherapy in cervical cancer patients.

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).

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).

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.