前列腺癌同步加量放疗dIMRT和RapidArc比较研究

目的 前列腺大分割照射与盆腔常规分割预防照射相结合的同步加量放疗可提高前列腺癌临床疗效,本研究比较固定野动态调强(dynamic intensity modulated radiotherapy,dIMRT)与快速旋转调强(RapidArc)在前列腺癌同步加量放疗中的剂量分布、治疗效率和执行精度的差异,为临床应用提供参考.方法 选取2013-01-04-2013-12-31在中山大学肿瘤防治中心行放疗的10例前列腺癌高危风险患者,靶区包括前列腺、精囊和盆腔淋巴结.以相同的剂量目标和优化参数分别设计9野dIMRT、单弧和双弧RapidArc同步加量治疗计划,分别用9F、1ARC和2ARC表示.比较分析3种计划的靶区剂量学特点,直肠、膀胱、小肠和双侧股骨头等危及器官的受照剂量及体积,机器跳数,治疗时间以及剂量验证通过率.结果 对于PTV1,9F的D2％为(69.37±0.89) Gy,D50％为(66.92±0.63) Gy,HI为0.09±0.02,CI为0.83±0.05;1ARC的D2％为(71.13±1.21) Gy,D50％为(68.50±0.76) Gy,HI为0.12±0.02,CI为0.74±0.07;9F均优于1ARC,差异均有统计学意义,P＜0.05;9F与2ARC的各参数差异均无统计学意义,P＞0.05.对于PTV2,9F的V5％为(99.45±0.78)％,优于1ARC的(99.35±1.28)％,差异有统计学意义,P＜0.05;9F与2ARC各参数的差异均无统计学意义,P＞0.05.对于膀胱Dmean,3组计划差异无统计学意义,P＞0.05;对于直肠V67.5Gy,9F与2ARC的差异无统计学意义,P＞0.05;对于左右股骨头Dmean,1ARC和2ARC低于9F,差异有统计学意义,P＜0.05;各OAR其余评价指标9F均低于1ARC和2ARC,差异均有统计学意义,P＜0.05.1ARC和2ARC相比于9F机器跳数平均减少了70.0％和67.2％,治疗时间平均缩短了81.7％和61.0％.9F、1ARC和2ARC的3％/3 mm标准的γ通过率分别为97.8％、98.9％和99.4％,差异均具有统计学意义,P＜0.05.结论 相比于dIMRT,RapidArc可显著提高治疗效率,其双弧计划具有相仿的靶区覆盖,但对膀胱、直肠和小肠的保护更差,dIMRT更适用于前列腺癌同步加量放射治疗.

Comparison of RapidArc and fixed gantry dynamic intensity modulated radiotherapy using simultaneous integrated boost for prostate cancer

OBJECTIVE A new IMRT simultaneous integrated boost strategy that irradiates prostate via hypofrac tionation while irradiating pelvic nodes with the conventional fractionation provide more benifits for high-risk prostate cancer.The aim of this study was to compare dose distribution,treatment efficiency and delivery accuracy between RapidArc and fixed gantry dynamic intensity modulated radiotherapy(dIMRT) using a simultaneous integrated boost for prostate cancer.METHODS Ten high-risk prostate cancer patients were selected from 4th Jan.2013 to 31st Dec.2013,in Sun Yat-sen University Cancer Center.The planning target volume(PTV) contained prostate,seminal vesicles,and pelvic lymph nodes with a margin.9F dIMRT(9F),single arc(1ARC) and two arc(2ARC) were designed respectively with the same dose objective and optimize parameters.The dose distribution of the targets and organs at risk(such as bladder,rectum,small bowel and bilateral femoral),monitor units,treatment time and pass ratios of dose verification were compared among the three kinds of plans.RESULTS The D2％ (69.37±0.89) Gy,D50％ (66.92±0.63) Gy,HI(0.09±0.02) and CI(0.83+0.05) of PTV1 in 9F were slightly better than those in 1ARC which were (71.13±1.21) Gy,(68.50+ 0.76) Gy,(0.12±0.02),(0.74±0.07),except D98％,the differences were significant(P＜0.05).All dosimetric indices of PTV1 in 9F and 2ARC were close and the difference were no significant(P＞0.05).The V95％ (99.45+0.78)％ of PTV2 in 9F was slightly better than that in 1ARC(99.35+ 1.28) ％,the difference was significant(P＜0.05).All dosimetric indices of PTV2 in 9F and 2ARC were close and the differences were not significant(P＞0.05).There were no significant differences for Dmean of bladder among all the three plans,for V67.5 Gy of rectum between 9F and 2ARC(P＞0.05).The Dmean of left and right femoral in 1ARC and 2ARC were lower than that in 9F,and the difference was significant(P＜ 0.05).Other dosimetric indices of OARs in 9F were lower than those in 1ARC and 2ARC,and much lower than 1ARC,the difference was significant(P＜0.05).The mean monitor units in 1ARC and 2ARC were fewer by 70.0％ and 67.2％ in comparison with that of 9F.The treatment mean time in 1ARC and 2ARC were shorter by 81.7％ and 61.0％ in com parison with 9F.The pass ratios of γ(3％/3 mm) from the verification were 97.8％ (9F),98.9％ (1ARC) and 99.4％ (2ARC),respectively,the differences were significant(P＜0.05).CONCLUSIONS Compared with dIMRT,RapidArc noticeably improved delivery efficiency,with two arcs provided comparable tumor dosimetric coverage,performed worse in dose sparing for bladder,rectum and small bowel.dIMRT plan is better than RapidArc in prostate cancer radiotherapy using a simultaneous integrated boost.