宫颈癌术后旋转拉弧适形和调强及三维适形放疗计划对比研究

Dosimetric study of Rapid Arc-SBRT,intensity-modulated radiotherapy and 3-dimensional conformal radiotherapy for postoperative cervical cancer

目的:通过宫颈癌术后旋转拉弧适形放疗(Rapid Arc stereotactic body radiotherapy,Rapid Arc-SBRT)、调强放疗(intensity-modulated radiotherapy,IMRT)和三维适形放疗(three-dimensional conformal radiotherapy,3D-CRT)技术的对比研究,比较应用不同外照射技术时计划靶区(planning target volume,PTV)剂量均匀度指数(homogeneity index HI)和适形度指数(conformity index,CI)的差异,以及PTV与其周围危及器官(organ at risk,OAR)受照剂量的差异,为3种技术能够更好地应用于临床提供剂量学参考。方法:随机选择2011-01-01-2011-12-31在中山大学附属佛山医院放疗科住院的10例宫颈癌术后患者,进行CT扫描、靶区和危及器官的勾画,处方剂量50Gy。分别进行Rapid ArcSBRT、IMRT和3D-CRT计划设计,计算靶区HI、CI、最大受照剂量(PTV Dmax)、最小受照剂量(PTV Dmin)、平均受照剂量(PTV Dmean)和OAR照射体积等并对结果进行比较分析。结果:IMRT和Rapid Arc-SBRT在靶区CI及在直肠、膀胱等危及器官的保护方面均优于3D-CRT,差异有统计学意义,P<0.05;Rapid Arc-SBRT计划在PTV Dmean方面要明显优于IMRT和3D-CRT计划,差异有统计学意义,P<0.05;右股骨头的V20,Rapid Arc-SBRT计划要明显优于IMRT计划,差异有统计学意义,P<0.05;膀胱受照射V20、V30、V40,IMRT计划要明显优于Rapid Arc-SBRT计划,差异有统计学意义,P<0.05。PTV Dmax、PTV Dmin、HI和OAR受照体积(小肠V10、V20、V30、V40,直肠V10、V20,膀胱V10,左、右股骨头V10、V30、V40)等方面,在3D-CRT、IMRT和Rapid Arc-SBRT计划之间的两两比较中,差异均无统计学意义,P>0.05。结论:宫颈癌术后辅助放疗IMRT和Rapid Arc-SBRT计划无论在靶区适形度还是正常组织保护方面均优于3D-CRT;同时也证实Rapid Arc-SBRT和IMRT计划在PTV Dmax、PTV Dmin、HI、CI和OAR(小肠、直肠、膀胱、股骨头)受照体积等方面有相似的剂量学优势,Rapid Arc-SBRT在PTV Dmean方面具有明显的优势。

OBJECTIVE： To compare the homogeneity index （HI） and conformity index （CI） of planning t^rget vol- ume（PTV） and the absorbed-dose of PTV and organ at risk （OAR） among three techniques, including Rapid Arc-SBRT, intensity-modulated radiotherapy （IMRT） and three-dimensional eonformal radiotherapy （3D-CRT）, which provide a do- simetric reference for patients with cervical cancer after radical hysterectomy. METHODS：Ten postoperative patients with cervical cancer from 1st Jan. 2011 to 31st Dec. 2011, in Foshan Hsopital Affiliated to Sun Yat-sen University, were cho- sen randomly. CT scan, PTV and OAR contouring were obtained. Rapid Arc-SBRT plan, IMRT plan and 3D-CRT plan were performed for each patient respectively, with the prescribed dose 50 Gy. Homogeneity index （HI）, conformity in- dex （CI）, maximum dose（Dmax）, minimum dose（Dman）, mean dose（Dmeman） of PTV and irradiated volume of OARs were calculated and the results were compared. RESULTS：Conformity index （CI） of PTV and protection of OARs in Rapid Arc-SBRT plan and IMRT plan were better than those in 3D-CRT plan. The difference was statistically significant （P〈0. 05）. Rapid Arc-SBRT plan had a better PTV Dmean, compared with IMRT and 3D-CRT. The difference was statistically significant （P〈0.05）. V2o of the right femoral head in Rapid Are-SBRT plan were better than those in IMRT plan. The differ- ence was statistically significant （P〈0. 05）. IMRT plan had a better V2o, V30, V40 of the bladder compared with Rapid Are-SBRT. The difference was statistically significant （P〈0.05）. There were no significant difference on the PTV Dmax, PTV Drain, HI and OAR （V10 ,V20 ,V30 ,V40 of the small bowel, V10 ,V20 of the rectum, Vio of the bladder, V10 ,V20 ,V40 of the left and right femoral head） among 3D-CRT, IMRT and Rapid Are-SBRT group （P〈0.05）. CONCLUCIONS： IMRT and Rapid Arc-SBRT plans are better than 3D-CRT plan in the CI of PTV and also better in sparing the OARs（rectum, bladder,etc）in the radiotherapy of postoperative cervical cancer. There are similar dosimetric advantages for Rapid Arc-SBRT and IMRT plan among the PTV Dmax, PTV Dein, HI, CI and irradiated volume of OARs（small bowel, rectum, bladder, femoral head）. Rapid Arc-SBRT plan has a more better PTV Dman, compared with IMRT.