宫颈癌术后延伸野螺旋断层放疗与固定野调强放疗剂量学比较

Comparison of dosimetry between extended-field helical therapy and fixed-field intensity-modulated radiation therapy for postoperative cervical cancer

目的:探讨宫颈癌术后延伸野螺旋断层放疗(helical therapy,HT)与固定野调强放疗(intensity-modulated radiation therapy,IMRT)计划靶区和危及器官(organ at risk,OAR)的剂量学特点。方法:收集重庆大学附属肿瘤医院2016年11月至2018年4月宫颈癌术后需行延伸野放疗的患者20例,由同一名医生勾画靶区和危及器官(膀胱、直肠、肠袋、股骨头、脊髓、肾脏),同一名物理师分别进行HT和IMRT计划设计。比较2种计划的靶区适形度指数(conformal index,CI)、均匀指数(homogeneity,HI)、OAR限量参数。结果:靶区HI指数HT组(0.06±0.02)明显好于IMRT组(0.09±0.03),差异有统计学意义(P=0.000);但靶区CI指数HT组(0.78±0.05)略低于IMRT组(0.92±0.04),差异有统计学意义(P=0.000)。OAR限量肠袋V40 Gy参数HT组[(120.97±83.46)cm3]大于IMRT组[(77.06±76.29)cm^3],且差异有统计学意义(P=0.000),其他限量HT组均优于IMRT组。靶区的剂量跌落指数(gradient index,GI)HT组明显优于IMRT组,差异有统计学意义(P=0.000),体内剂量在30%~50%范围内跌落更明显。结论:宫颈癌术后延伸野放疗采用HT和IMRT均能满足临床需求,但HT靶区均匀性更好。当对特定危及器官有更高保护需求时,HT更具有优势。

Objective:To compare the dosimetric difference of target areas and organs-at-risk(OAR)between extended-field tomosynthesis(HT)and fixed-field intensity-modulated radiation therapy(IMRT)for postoperative cervical cancer.Methods:Twenty patients with extended-field HT who underwent cervical cancer radical surgery from November 2016 to April 2018 in Chongqing University Cancer Hospital were enrolled.The same doctor outlined the target area and OARs(bladder,rectum,intestine bags,the femoral heads,spinal cord and kidneys)and the same physicist designed the HT and IMRT plans separately.Conformity index(CI)of target area,homogeneity(HI),and OAR parameters of two plans were compared.Results:The HI parameter in the HT group(0.06±0.02)was significantly better than that in the IMRT group(0.09±0.03),with statistically significant difference(P=0.000),but the CI parameter in the HT group(0.78±0.05)was slightly lower than that in the IMRT group(0.92±0.04),with statistically significant difference(P=0.000).OAR parameters in the HT group were superior to those in the IMRT group,except the V40 Gyof intestine pouch in the HT group(83.46 cm^3)was greater than that in the IMRT group of 76.29 cm3,with statistically significant difference(P=0.000).The gradient index(GI)parameter in the HT group was significantly superior to than that in the IMRT group,with statistically significant difference(P=0.000),and the drop in the internal dose was more obvious in the range of 30%to 50%.Conclusion:Both HT and IMRT can meet the clinical needs,but HI of HT has better homogeneity.HT has a preferable advantage for protecting OAR.