摘要目的 评估外照射后体积仍较大宫颈癌行三维腔内近距离放疗同步体外施源器引导下IMRT剂量学可行性.方法 用Oncentra4.3 TPS为7例外照射后体积较大的宫颈癌患者分别设计内外融合放疗计划和三维腔内放疗计划;并对同一患者4次内外融合放疗计划进行基于弹性配准的三维剂量叠加,计算OAR累积剂量,使用配对t检验或Wilcoxon符号秩检验差异.结果 内外融合计划D90、V100、CI高于三维腔内计划(P=0.000);两种计划直肠、乙状结肠和膀胱D2cc差异无统计学意义(P>0.05);弹性配准三维剂量叠加法与DVH参数数值相加法两种OAR累积剂量计算方法计算直肠、乙状结肠、膀胱总D2cc值差异无统计学意义(P>0.05).结论 对外照射后体积仍较大的宫颈癌,内外融合放疗可显著提高靶区覆盖和适形度,并未明显增加OAR剂量.验证了三维叠加法与数值相加法对OAR累积剂量的评估方法的可行性.

abstractsObjective 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.