A treatment planning study comparing volumetric arc modulation with RapidArc and fixed field IMRT for cervix uteri radiotherapy
A treatment planning study comparing volumetric arc modulation with RapidArc and fixed field IMRT for cervix uteri radiotherapy
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DOI：
10.1016/j.radonc.2008.06.013
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发表时间：
2008-11-01
影响因子：
5.7
通讯作者：
Fogliata, Antonella
中科院分区：
文献类型：
--
作者：
Cozzi, Luca;Dinshaw, Ketayun Ardeshir;Fogliata, Antonella
目的：通过一项治疗计划研究，评价新型容积调节式单弧放射治疗宫颈癌患者的疗效。以常规固定野调强放疗为基准。方法和材料：本研究包括8例患者的CT数据。优化了计划，目的是评估处于危险中的器官和健康组织的保留，同时执行高度适形的目标覆盖。计划目标为：最大有效剂量低于52.5Gy，最小有效剂量大于47.5Gy.对于有危险的器官，中位剂量和最大剂量被限制在30(直肠)、35(膀胱)、25(小肠)和47.5Gy以下；其他目标设定在不同的体积阈值上。根据剂量体积直方图得出的参数和NTCP估计对计划进行评估。在距PTV表面5、10和15 cm处记录周边剂量，以评估低剂量浴。结果：RapidArc和IMRT的靶点覆盖率相当，但RapidArc的均质性(D-5%-D-95%=3.5+/-0.6GyRapidArc和IMRT为4.3+/-0.8Gy.)和符合指数(CI90%=1.30+/-0.06和1.41+/-0.15)均有改善。在直肠，平均剂量减少了约6GY(直肠部分不包括在PTV中的10GY)。不同的剂量水平也观察到了类似的趋势，降幅从类似的3到14.4Gy.对于膀胱，RapidArc允许将平均剂量从类似的4到6GY减少到类似的3到9GyW.r.t。调强放射治疗。在小肠和左侧和右侧股骨也观察到了类似的趋势，但绝对差异较小。对膀胱和直肠的NTCP计算证实了DVH数据，从调强放疗到RapidArc，潜在的相对减少幅度为30%到70%。健康组织在中到高剂量区域(从20到30GY)受到的照射明显减少，与调强放疗相比，RapidArc的整体剂量减少了约12%。在周边剂量方面，调强放疗与RapidArc在距PTV表面5、10和15 cm处的相对差值分别为9+/-2%、43+/-11%和36+/-5%。RapidArc的MU/Gy245+/-17，相当于预期的平均照射时间为73+/-10 S/2Gy.调强放射治疗计划显示出较高的数值，平均MU/GY=479+/-63。结论：RapidArc在宫颈癌研究中显示出危险器官和健康组织的显著改善，目标覆盖范围不受影响，从而更好地适形避免了治疗。常规调强放射治疗。这一点，再加上确认的较短的分娩时间，可以导致这种高度侵袭性癌症类型的管理在临床上取得重大进展。现在建议临床方案前瞻性地评估在规划水平观察到的潜在益处。(C)2008爱思唯尔爱尔兰有限公司。保留所有权利。放射治疗和肿瘤学89(2008)180-191。
Purpose: A treatment planning study was performed to evaluate the performance of the novel volumetric modulated single arc radiotherapy on cervix uteri cancer patients. Conventional fixed field IMRT was used as benchmark.Methods and materials: CT datasets of eight patients were included in the study. Plans were optimised with the aim to assess organs at risk and healthy tissue sparing while enforcing highly conformal target coverage. Planning objectives for PTV were: maximum significant dose lower than 52.5 Gy and minimum significant dose higher than 47.5 Gy. For organs at risk, the median and maximum doses were constrained to be lower than 30 (rectum), 35 (bladder) and 25 Gy (small bowel) and 47.5 Gy; additional objectives were set on various volume thresholds. Plans were evaluated on parameters derived from dose volume histograms and on NTCP estimates. Peripheral doses at 5, 10 and 15 cm from the PTV surface were recorded to assess the low-level dose bath. The MU and delivery time were scored to measure expected treatment efficiency.Results: Both RapidArc and IMRT resulted in equivalent target coverage but RapidArc had an improved homogeneity (D-5%-D-95% = 3.5 +/- 0.6 Gy for RapidArc and 4.3 +/- 0.8 Gy for IMRT) and conformity index (CI90% = 1.30 +/- 0.06 for RapidArc and 1.41 +/- 0.15 for IMRT). On rectum the mean dose was reduced by about 6 Gy (10 Gy for the rectum fraction not included in the PTV). Similar trends were observed for the various dose levels with reductions ranging from similar to 3 to 14.4 Gy. For the bladder, RapidArc allowed a reduction of mean dose ranging from similar to 4 to 6 Gy and a reduction from similar to 3 to 9 Gy w.r.t. IMRT. Similar trends but with smaller absolute differences were observed for the small bowel and left and right femur. NTCP calculations on bladder and rectum confirmed the DVH data with a potential relative reduction ranging from 30 to 70% from IMRT to RapidArc. The healthy tissue was significantly less irradiated in the medium to high dose regions (from 20 to 30 Gy) and the integral dose reduction with RapidArc was about 12% compared to IMRT. Concerning peripheral dose, the relative difference between IMRT and RapidArc was of 9 +/- 2%, 43 +/- 11% and 36 +/- 5% at 5, 10 and 15 cm from the PTV surface, respectively. The MU/Gy from RapidArc was 245 +/- 17 corresponding to an expected average beam on time of 73 +/- 10 s per fractions of 2 Gy. IMRT plans presented higher values with an average of MU/Gy = 479 +/- 63.Conclusion: RapidArc was investigated for cervix uteri cancer showing significant improvements in organs at risk and healthy tissue sparing with uncompromised target coverage leading to better conformal avoidance of treatments w.r.t. conventional IMRT. This, in combination with the confirmed short delivery time, can lead to clinically significant advances in the management of this highly aggressive cancer type. Clinical protocols are now advised to evaluate prospectively the potential benefit observed at the planning level. (c) 2008 Elsevier Ireland Ltd. All rights reserved. Radiotherapy and Oncology 89 (2008) 180-191.