Kannarunimit Danita, Descovich Martina, Garcia Aaron, Chen Josephine, Weinberg Vivian, Mcguinness Christopher, Pinnaduwage Dilini, Murnane John, Gottschalk Alexander R, Yom Sue S
Department of Radiation Oncology, King Chulalongkorn University Hospital, Bangkok.
Department of Radiation Oncology, University of California, San Francisco.
Technol Cancer Res Treat. 2015 Feb;14(1):49-60. doi: 10.7785/tcrt.2012.500394. Epub 2014 Nov 11.
Stereotactic body radiation therapy (SBRT) to central lung tumors is associated with normal -tissue toxicity. Highly conformal technologies may reduce the risk of complications. This study compares physical dose characteristics and anticipated risks of radiation pneumonitis (RP) among three SBRT modalities: robotic radiosurgery (RR), helical tomotherapy (HT) and volumetric modulated arc therapy (VMAT). Nine patients with central lung tumors ≤5 cm were compared. RR, HT and VMAT plans were developed per RTOG 0831. Dosimetric comparisons included target coverage, conformity index, heterogeneity index, gradient index, maximal dose at 2 cm from target (D2 cm), and dose-volume parameters for organs at risk (OARs). Efficiency endpoints included total beam-on time and monitor units. RP risk was derived from Lyman-Kutcher-Burman modeling on in-house software. The average GTV and PTV were 11.6 ± 7.86 cm(3) and 36.8 ± 18.1 cm(3). All techniques resulted in similar target coverage (p = 0.64) and dose conformity (p = 0.88). While RR had sharper fall-off gradient (p = 0.002) and lower D2 cm (p = 0.02), HT and VMAT produced greater homogeneity (p < 0.001) and delivery efficiency (p = 0.001). RP risk predicted from whole or contralateral lung volumes was less than 10%, but was 2-3 times higher using ipsilateral volumes. Using whole (p = 0.04, p = 0.02) or ipsilateral (p = 0.004, p = 0.0008) volumes, RR and VMAT had a lower risk of RP than HT. Using contralateral volumes, RR had the lowest RP risk (p = 0.0002, p = 0.0003 versus HT, VMAT). RR, HT and VMAT were able to provide clinically acceptable plans following the guidelines provided by RTOG 0813. All techniques provided similar coverage and conformity. RR seemed to produce a lower RP risk for a scenario of small PTV-OAR overlap and small PTV. VMAT and HT produced greater homogeneity, potentially desirable for a large PTV-OAR overlap. VMAT probably yields the lowest RP risk for a large PTV. Understanding subtle differences among these technologies may assist in situations where multiple choices of modality are available.
对中央型肺肿瘤进行立体定向体部放射治疗（SBRT）会伴有正常组织毒性。高度适形技术可能会降低并发症风险。本研究比较了三种SBRT模式：机器人放射外科（RR）、螺旋断层放射治疗（HT）和容积调强弧形治疗（VMAT）的物理剂量特征以及放射性肺炎（RP）的预期风险。对9例中央型肺肿瘤≤5 cm的患者进行了比较。根据RTOG 0831制定RR、HT和VMAT计划。剂量学比较包括靶区覆盖、适形指数、不均匀性指数、梯度指数、距靶区2 cm处的最大剂量（D2 cm）以及危及器官（OARs）的剂量体积参数。效率终点包括总照射时间和监测单位。RP风险通过内部软件上的Lyman-Kutcher-Burman模型得出。平均大体肿瘤体积（GTV）和计划靶体积（PTV）分别为11.6±7.86 cm³和36.8±18.1 cm³。所有技术的靶区覆盖（p = 0.64）和剂量适形性（p = 0.88）相似。虽然RR的剂量下降梯度更陡（p = 0.002）且D2 cm更低（p = 0.02），但HT和VMAT的均匀性更好（p < 0.001）且治疗效率更高（p = 0.001）。根据全肺或对侧肺体积预测的RP风险小于10%，但使用同侧肺体积时则高2至3倍。使用全肺（p = 0.04，p = 0.02）或同侧肺体积（p = 0.004，p = 0.0008）时，RR和VMAT的RP风险低于HT。使用对侧肺体积时，RR的RP风险最低（与HT、VMAT相比，p = 0.0002，p = 0.0003）。RR、HT和VMAT能够按照RTOG 0813提供的指南制定出临床可接受的计划。所有技术的覆盖和适形性相似。对于PTV与OAR重叠小且PTV小的情况，RR似乎产生的RP风险更低。对于PTV与OAR重叠大的情况，VMAT和HT的均匀性更好，这可能是有利的。对于大PTV，VMAT可能产生的RP风险最低。了解这些技术之间的细微差异可能有助于在有多种模式可供选择的情况下做出决策。
