A dosimetric study of 3D intracavitary brachytherapy in combination with applicator-guided IMRT boost for cervical cancer / 中华放射肿瘤学杂志

ABSTRACT

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 system3D 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 usedsimple 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.