两种容积旋转调强方法在局部晚期直肠癌术前放疗的剂量学比较

Dosimetric comparison of two RapidArc delivery strategies in preoperative short-course radiotherapy for locally advanced rectal cancer

目的研究不同容积旋转调强方法对局部晚期直肠癌术前短程放疗病例的剂量学影响。方法选择Ⅱ~Ⅲ期直肠癌病例16例,使用容积弧形调强放射治疗技术(RapidArc)对每个病例分别进行双全弧(FAAS)和双半弧(PA,150°~210°)的计划设计,比较两种计划下的靶区和危及器官各剂量参数以及总机器跳数(MU)。结果两种设计的计划靶区(PTV)接受2325 cGy的照射体积(V_(2325cGy))、最小剂量(D_(min))、最大剂量(D_(max))、靶区适形指数(CI)、靶区剂量均匀性指数(HI)差异有统计学意义(P<0.05);FAAS中大肠、膀胱、盆腔骨髓、左右股骨头的平均剂量(D_(mea)n)较PA明显降低,差异有统计学意义(P<0.05);总机器MU差异有统计学意义(P<0.05);其余指标差异无统计学意义(P>0.05)。结论在局部晚期直肠癌接受术前短程放疗Rapid Arc计划设计时,选择FAAS可以保证靶区剂量的适形度和均匀性,减少危及器官的受量,降低总MU输出。

Objective To evaluate the dosimetric impact of two RapidArc delivery strategies in preoperative short-course ra- diotherapy for locally advanced rectal cancer. Methods Sixteen patients with stage Ⅱ - Ⅲ rectal cancer were selected for this study. Two RapidAre plans were generated for the patients using full arc with avoidance sectors （FAAS） and partial arc （PA） techniques ,re- spectively. Dosimetry of the target and organs at risk （ OARs ） and monitor unit （ MU ） were statistically analyzed. Results The W2325cGy, Drain, D conformity index （ CI）, homogeneity index （HI） of the planning target volume （PTV） of the two strategies was sig- nificantly different （P 〈 0. 05）. The mean level of irradiation doses to the big bowel,bladder,bone marrow,femur heads and total MU in the FAAS technique were significantly lower when compared to the PA plan （P 〈 0. 05 ）. However, the differences in other parameters was not significant between the two plans （P 〉 0. 05 ）. Conclusion This study suggests that the FAAS technique is more beneficial for patients with locally advanced rectal cancer undergoing preoperative short-course radiotherapy. It is reflected in better conformal and homogeneous dose to the target and reduction in the irradiated dose to OAR than PA plan.