Dosimetric impacts of multichannel applicator in three-dimensional brachytherapy for advanced cervical carcinoma

Objective: To investigate the relationship between the channel design of tandem- and-ovoid (T&O) applicator and the doses to organs at risk (OARs) and target volume in three-dimensional brachytherapy for advanced cervical carcinoma. Methods: The data on 15 patients with advanced cervical carcinoma treated with three-dimensional brachytherapy in our hospital from 2015 to 2016 were collected, and 30 randomly selected high-dose-rate titanium T&O plans were retrospectively studied. CT-guided, conformal brachytherapy plans were generated. To simulate T&O applicator, the tandem applicator was virtually compared with the T&O plans with the target volume and OARs remaining unchanged. The DVH parameters of the rectum, bladder, and sigmoid were compared using the paired t test. Results: For T&O plans and tandem applicator plans, the mean D_2cc of the rectum was 387.8 ± 96.8 cGy and 340.8 ± 88.1 cGy, respectively; the mean D_2cc of the bladder was 443.2 ± 87.5 cGy and 719.4 ± 243.0 cGy, respectively; the mean D_2cc of the sigmoid was 330.3 ± 88.8 cGy and 383.1 ± 105.6 cGy, respectively. In the T&O plans, the doses to the rectum, bladder, and sigmoid were within the limits (rectum; D_2cc ≤ 500 cGy; bladder: D_2cc ≤ 550 cGy; sigmoid: D_2cc ≤ 500 cGy), while D_2cc of the bladder and sigmoid was higher or partially higher than the limits. T&O plans showed a significant reduction in bladder D_2cc and sigmoid D_2cc compared with the tandem applicator plans (all P < 0.05). Conclusions: Compared with tandem applicator plans, plans using T&O applicator provide significant sparing of bladder and sigmoid tissues in three-dimensional brachytherapy for cervical carcinoma, but the toxicities require further investigation. (authors)