Dose heterogeneity in the target volume and intensity-modulated radiotherapy to escalate the dose in the treatment of non-small-cell lung cancer
Dose heterogeneity in the target volume and intensity-modulated radiotherapy to escalate the dose in the treatment of non-small-cell lung cancer
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DOI：
10.1016/j.ijrobp.2005.02.011
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发表时间：
2005-06-01
影响因子：
7
通讯作者：
Damen, EMF
中科院分区：
文献类型：
--
作者：
Schwarz, M;Alber, M;Damen, EMF
目的：通过允许靶区剂量异质性或使用调强放射治疗 (IMRT) 或两者同时使用，量化非小细胞肺癌 (NSCLC) 治疗中可实现的剂量递增。方法和材料：本研究选择了 10 名肿瘤运动受限且代表广泛临床病例的 NSCLC 患者的计算机断层扫描数据和轮廓。比较了四种照射技术：两种适形 (CRT) 和两种 IMRT 技术，要么在计划目标体积 (PTV) 中规定均匀剂量（CRThom 和 IMRThom），要么允许剂量异质性（CRTinhom 和 IMRTinhom）。仅允许高剂量存在剂量异质性，即 CRTinhom 和 IMRTinhom 目标中的最小剂量不能低于相应的同质计划。 PTV 中的剂量逐渐增加（分数大小为 2.25 Gy），直到有风险的器官达到最大允许剂量或平均 PTV 剂量达到设定为 101.25 Gy 的最大水平。结果：当照射小型凸形肿瘤时，CRThom 可以达到 101.25 Gy 的最大剂量，而对于较大和/或凹形 PTV，CRThom 可实现的剂量水平明显较低， 1例低于60Gy。相对于 CRThom，CRTinhom 允许平均增加 6% 的剂量。除 1 例外，所有 IMRThom 均达到至少 75 Gy 的平均 PTV 剂量。 IMRThom 相对于 CRThom 的平均 PTV 剂量增益范围为 7.7 至 14.8 Gy，并且 IMRThom 计划始终比相应的 CRThom 计划更适形。 IMRTinhom 比 IMRThom 具有至少 5 Gy 的额外优势。对于所有 CRT 计划，可达到的剂量由肺剂量阈值决定，而对于一半以上的 IMRT 计划，食道是剂量限制器官。 IMRT 计划可通过每束 10-12 个节段进行交付，并且不会增加低剂量 (< 20 Gy) 照射下的肺体积。 结论： NSCLC 治疗中的剂量可以通过放宽对靶区最大剂量的限制或使用 IMRT 或两者兼而有之来增加。对于大型和凹形肿瘤，单独应用剂量异质性和 IMRT 时，平均剂量可能增加 6% 和 17%。当它们结合使用时，平均剂量增加高达 35%。以静态模式进行的强度调制放疗可以在靶区产生均匀的剂量分布，并且不会导致接受（非常）低剂量（甚至低至 5 Gy）的肺容量增加。 (c) 2005 年爱思唯尔公司。
Purpose: To quantify the dose escalation achievable in the treatment of non-small-cell lung cancer (NSCLC) by allowing dose heterogeneity in the target volume or using intensity-modulated radiotherapy (IMRT), or both.Methods and Materials: Computed tomography data and contours of 10 NSCLC patients with limited movements of the tumor and representing a broad spectrum of clinical cases were selected for this study. Four irradiation techniques were compared: two conformal (CRT) and two IMRT techniques, either prescribing a homogeneous dose in the planning target volume (PTV) (CRThom and IMRThom) or allowing dose heterogeneity (CRTinhom and IMRTinhom). The dose heterogeneity was allowed only toward high doses, i.e., the minimum dose in the target for CRTinhom and IMRTinhom could not be lower than for the corresponding homogeneous plan. The dose in the PTV was escalated (fraction size of 2.25 Gy) until either an organ at risk reached the maximum allowed dose or the mean PTV dose reached a maximum level set at 101.25 Gy.Results: When small and convex tumors were irradiated, CRThom could achieve the maximum dose of 101.25 Gy, whereas for bigger and/or concave PTVs the dose level achievable with CRThom was significantly lower, in 1 case even below 60 Gy. The CRTinhom allowed on average a 6% dose escalation with respect to CRThom. The IMRThom achieved in all except 1 case a mean PTV dose of at least 75 Gy. The gain in mean PTV dose of IMRThom with respect to CRThom ranged from 7.7 to 14.8 Gy and the IMRThom plans were always more conformal than the corresponding CRThom plans. The IMRTinhom provided an additional advantage over IMRThom of at least 5 Gy. For all CRT plans the achievable dose was determined by the lung dose threshold, whereas for more than half of the IMRT plans the esophagus was the dose-limiting organ. The IMRT plans were deliverable with 10-12 segments per beam and did not produce an increase of lung volume irradiated at low doses (< 20 Gy).Conclusions: The dose in NSCLC treatments can be escalated by loosening the constraints on maximum dose in the target volume or using IMRT, or both. For large and concave tumors, an average dose escalation of 6% and 17% was possible when dose heterogeneity and IMRT were applied alone. When they were combined, the average dose increase was as high as 35%. Intensity-modulated RT delivered in a static mode can produce homogeneous dose distributions in the target and does not lead to an increase of lung volume receiving (very) low doses, even down to 5 Gy. (c) 2005 Elsevier Inc.