Résumé
Objective To evaluate the dosimetric feasibility of three-dimensional(3D)intracavitary brachytherapy in combination with applicator-guided intensity-modulated radiation therapy(IMRT)boost for patients with locally advanced cervical cancer who have unfavorable topography following external beam irradiation. Methods A total of 7 patients with locally advanced cervical cancer who had unfavorable topography following external beam irradiation were included. Two plans were generated for brachytherapy using Oncentra 4.3 treatment planning system:3D intracavitary brachytherapy and 3D intracavitary brachytherapy in combination with applicator-guided IMRT boost.To further evaluate cumulative doses to organs at risk(OAR)in the four fractions of combined plans,two methods were used:simple dose-volume histograms(DVH)parameter addition and deformable image registration(DIR)-based DVH accumulation. The D90, V100, and conformity index(CI)were evaluated. The paired t-test or Wi1coxon signed rank test was used for statistical analysis. Results Compared with the 3D plan,the combined plan yielded higher D90, V100, and CI(P=0.000), but showed no significant difference in D2ccof the rectum,sigmoid colon,and bladder(P>0.05). There were also no significant differences in D2ccof the rectum, sigmoid colon, and bladder calculated by the two methods for calculating OAR cumulative doses, simple DVH parameter addition and DIR-based DVH accumulation(P>0.05). Conclusions For patients with cervical cancer who have unfavorable topography following external beam irradiation,3D intracavitary brachytherapy in combination with applicator-guided IMRT boost can improve target coverage and CI, without increasing OAR doses. DIR-based DVH accumulation and simple DVH parameter addition may be both acceptable for assessing OAR cumulative doses.
Résumé
Objective To investigate the relationship between the channel design of tandem-andovoid (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 D2cc of the rectum was 387.8±96.8 cGy and 340.8±88.1 cGy,respectively;the mean D2cc of the bladder was 443.2± 87.5 cGy and 719.4± 243.0 cGy,respectively;the mean D2cc 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:D2cc ≤ 500 cGy;bladder:D2cc ≤ 550 cGy;sigmoid:D2c ≤ 500 cGy),while D2cc of the bladder and sigmoid was higher or partially higher than the limits.T&O plans showed a significant reduction in bladder D2cc and sigmoid D2cc 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.