非小细胞肺癌NCCN指南2017第5版：放射治疗原则

PRINCIPLES OF RADIATION THERAPY放射治疗原则

General Principles (see Table 1. Commonly Used Abbreviations in Radiation Therapy)一般原则（见表1。放射治疗常用缩写）

* Determination of the appropriateness of radiation therapy (RT) should be made by board-certified radiation oncologists who perform lung cancer RT as a prominent part of their practice. 应该由通过职业认证、临床实践中主要从事肺癌放疗的放射肿瘤学家确定合理的放疗（RT）。山东省肿瘤医院呼吸肿瘤内科张品良

* RT has a potential role in all stages of NSCLC, as either definitive or palliative therapy. Radiation oncology input as part of a multidisciplinary evaluation or discussion should be provided for all patients with NSCLC. 作为根治性或姑息性治疗，在所有分期的非小细胞肺癌中放疗均有一定地位。放射肿瘤学作为多学科评估或讨论的一部分，对所有非小细胞肺癌患者均应提供。

* The critical goals of modern RT are to maximize tumor control and to minimize treatment toxicity. A minimum technologic standard is CT-planned 3D-CRT. 现代放疗的关键目的是肿瘤控制最大化，同时使治疗毒性最小化。最低技术标准是根据CT设计的三维适形放疗。

* More advanced technologies are appropriate when needed to deliver curative RT safely. These technologies include (but are not limited to) 4D-CT and/or PET/CT simulation, IMRT/VMAT, IGRT, motion management, and proton therapy (https://www.astro.org/Daily-Practice/Reimbursement/Model-Policies/Model-Policies/). Nonrandomized comparisons of using advanced technologies versus older techniques demonstrate reduced toxicity and improved survival. In a prospective trial of definitive chemo/RT for stage III NSCLC (RTOG 0617), IMRT was associated with a nearly 60% decrease in high-grade radiation pneumonitis and similar survival and tumor control outcomes despite a higher proportion of stage IIIB and larger treatment volumes compared to 3D-CRT; as such, IMRT is preferred over 3D-CRT in this setting.当需要安全的根治性放疗时，可合理使用更先进的技术。这些技术包括（但不限于）4D-CT和/或PET/CT模拟、IMRT（调强放疗）/VMAT（旋转容积调强放疗）、IGRT（影像引导放射治疗技术）、运动管理及质子治疗（https://www.astro.org/Daily-Practice/Reimbursement/Model-Policies/Model-Policies/）。采用先进技术与老旧技术的非随机对照证明，降低毒性并改善生存。在一项根治性化/放疗治疗Ⅲ期非小细胞肺癌的前瞻性试验（RTOG 0617）中，与三维适形放疗相比，尽管调强放疗组ⅢB期比例较高且治疗体积较大，但是，调强放疗降低高级别放射性肺炎近60%而生存和肿瘤控制结果相似；因此，在这种情况下，适形调强放疗优于三维适形放疗。

* Centers using advanced technologies should implement and document modality-specific quality assurance measures. The ideal is external credentialing of both treatment planning and delivery such as required for participation in RTOG clinical trials employing advanced technologies. Useful references include the ACR Practice Parameters and Technical Standards (http://www.acr.org/~/media/ACR/Documents/PGTS/toc.pdf).使用先进技术的中心应实施并记录具体的质量保证措施。治疗计划与交付两者均外部认证是理想的，就像RTOG临床试验采用先进技术所要求的那样。有用的参考文献包括美国放射学会实践参数与技术标准(http://www.acr.org/~/media/ACR/Documents/PGTS/toc.pdf)。

Early-Stage NSCLC (Stage I, selected node negative Stage IIA)早期非小细胞肺癌（I期，某些淋巴结阴性的ⅡA期）

* SABR (also known as SBRT) is recommended for patients who are medically inoperable or who refuse to have surgery after thoracic surgery evaluation. SABR has achieved primary tumor control rates and overall survival, comparable to lobectomy and higher than 3D-CRT in nonrandomized and population-based comparisons in medically inoperable or older patients. 对于那些因内科因素不能手术或在开胸评价术后拒绝手术的患者，推荐立体定向消融放疗（SABR）（也称为SBRT）。在非随机和以人群为基础的对比中，因内科因素不能手术或老年患者，立体定向消融放疗（SABR）获得的原发肿瘤控制率和总生存率可媲美肺叶切除术且优于三维适形放疗。

* SABR is also an appropriate option for patients with high surgical risk (able to tolerate sublobar resection but not lobectomy [eg, age ≥75 years], poor lung function). SABR and sublobar resection achieve comparable cancer-specific survival and primary tumor control. 立体定向消融放疗（SABR）也是手术风险较高（能够耐受亚肺叶切除而非肺叶切除术[如年龄≥75岁]、肺功能差）患者的一个合适选择。立体定向消融放疗（SABR）达到的癌症特异性生存和原发肿瘤控制可媲美亚肺叶切除。

* A combined analysis of two randomized trials (that individually did not complete accrual) of SABR vs. lobectomy in operable patients found similar cancer-specific outcomes and improved toxicity profile and survival for SABR compared to surgery. This analysis does not provide sufficient data to change the standard of care for good surgical candidates but strengthens the indication for SABR in patients with relative contraindications for surgery or who refuse surgery.比较立体定向消融放疗（SABR）与肺叶切除术治疗可手术患者的两项随机试验（单独未完成入组）的联合分析发现，与手术相比，SABR具有类似的癌症特异性结局，并且，SABR改善毒性和生存。该分析并未提供充分的数据改变良好手术候选者的治疗标准，但加强了立体定向消融放疗（SABR）治疗具有手术相对禁忌症或拒绝手术的患者的指征。

* For institutions without an established SABR program, more modestly hypofractionated or dose-intensified conventionally fractionated 3D-CRT regimens are less preferred alternatives.由于协会没有制定立体定向消融放疗方案，因此，更适度的超分割或剂量加强的常规分割三维适形放疗方案是次优替代选择。

* In patients treated with surgery, postoperative radiotherapy (PORT) is not recommended unless there are positive margins or upstaging to N2 (see Locally Advanced NSCLC in this section).在接受手术的患者中，不推荐术后放疗（PORT），除非是切缘阳性或升期为N2（见本节中的局部晚期非小细胞肺癌）。

Locally Advanced NSCLC (Stage II-III)局部晚期非小细胞肺癌（Ⅱ-Ⅲ期）

* The standard of care for patients with inoperable stage II (node positive) and stage III is concurrent chemotherapy/RT. *不能手术的Ⅱ期（淋巴结阳性）和Ⅲ期患者的标准治疗是同步化/放疗。

RT interruptions and dose reductions for manageable acute toxicities should be avoided by employing supportive care. 通过采用支持治疗处理急性毒性，应避免放疗中断和减量。

* Sequential chemotherapy/RT or RT alone is appropriate for frail patients unable to tolerate concurrent therapy. 序贯化/放疗或单纯放疗适于无法耐受同步治疗的体弱患者。

Accelerated RT regimens may be beneficial, particularly if concurrent chemotherapy would not be tolerated (ie, in a sequential or RT-only approach).加速放疗方案可能是有益的，特别是如果同步化疗不能耐受（即，以序贯或单纯放疗的方式）。

* RT has a role before or after surgery. 术前或术后放疗都有地位。

▶ Preoperative concurrent chemotherapy/RT is an option for patients with resectable stage IIIA (minimal N2 and treatable with lobectomy) and is recommended for resectable superior sulcus tumors. 对于可切除的ⅢA期（最低限度的N2且可肺叶切除治疗）患者，术前同步化/放疗是一个选择，并推荐用于可切除的肺上沟瘤。

▶ Preoperative chemotherapy and postoperative RT is an alternative for patients with resectable stage IIIA. The optimal timing of RT in trimodality therapy (preoperative with chemotherapy or postoperative) is not established and is controversial. 对于可切除的ⅢA期患者，术前化疗和术后放疗是一个备选方案。在三联疗法（术前或术后化疗）中，无公认的放疗最佳时机，是有争议的。

▶ The determination of resectability in trimodality therapy should be made prior to initiation of all treatment. Upfront multidisciplinary consultation is particularly important when considering surgical treatment of stage III NSCLC. 在三联疗法中，应该在所有治疗开始之前确定可切除性。当考虑Ⅲ期非小细胞肺癌外科治疗时，前期多学科会诊是特别重要的。

▶ In patients with clinical stage I/II upstaged surgically to N2+, PORT appears to improve survival significantly as an adjunct to postoperative chemotherapy in non-randomized analyses. Although the optimal sequence is not established, PORT is generally administered after postoperative chemotherapy. PORT with concurrent chemotherapy can be administered safely in medically fit patients and is recommended for positive resection margins.临床I/Ⅱ期、手术升期至N2+的患者，多项非随机分析认为，术后放疗（PORT）作为术后化疗的辅助手段似乎显著改善生存。虽然无公认的最佳顺序，但是，术后放疗（PORT）通常在术后化疗后给予。术后放疗（PORT）同时化疗可安全实施，在医学上的患者，并建议积极切除边缘。

▶ PORT is not recommended for patients with pathologic stage N0-1 disease, because it has been associated with increased mortality, at least when using older RT techniques. 对于病理分期N0-1的患者，不推荐术后放疗（PORT），因为已发现与死亡率增加有关，起码在使用老的放疗技术时是这样。

Advanced/Metastatic NSCLC (Stage IV)晚期/转移性非小细胞肺癌（Ⅳ期）

* RT is recommended for local palliation or prevention of symptoms (such as pain, bleeding, or obstruction).推荐放疗用于缓解或预防局部症状（如疼痛、出血或梗阻）。

* Definitive local therapy to isolated or limited metastatic sites (oligometastases) (including but not limited to brain, lung, and adrenal gland) achieves prolonged survival in a small proportion of well-selected patients with good performance status who have also received radical therapy to the intrathoracic disease. Definitive RT to oligometastases, particularly SABR, is an appropriate option in such cases if it can be delivered safely to the involved sites.对孤立或局限的转移部位（寡转移）（包括但不限于脑、肺、肾上腺）根治性局部治疗，在一小部分精心挑选的、一般状况良好、胸内病变也已经接受根治性治疗的患者中，可延长生存期。对寡转移根治性放疗，特别是立体定向放疗消融（SABR），如果对受累部位可以安全地实施，在这种情况下是一个合适的选择。

* See the NCCN Guidelines for Central Nervous System Cancers regarding RT for brain metastases.见中枢神经系统肿瘤有关脑转移瘤放疗NCCN指南。

Target Volumes, Prescription Doses, and Normal Tissue Dose Constraints (See Tables 2–5 on NSCL-C 7 of 10 and NSCL-C 8 of 10)靶体积、处方剂量和正常组织剂量限制（见NSCL-C7/10和NSCL-C8/10中的表2–5）

* ICRU Reports 62 and 83 detail the current definitions of target volumes for 3D-RT and IMRT. GTV comprises the known extent of disease (primary and nodal) on imaging and pathologic assessment, CTV includes regions of presumed microscopic extent or dissemination, and PTV comprises the ITV (which includes margin for target motion) plus a setup margin for positioning and mechanical variability. 国际辐射单位与测量委员会（ICRU）62和83报告详述了目前三维放疗和适形调强放疗靶体积的定义。大体靶区（GTV）包括在影像学和病理学评估时已知的病变范围（原发灶和淋巴结），临床靶区（CTV）包括推测的微观范围或播散区域，而计划靶区（PTV）包括靶区运动范围（ITV）（包括目标运动的边界）加定位与机械设备变化（误差）调整的边界。

http://www.rtog.org/CoreLab/ContouringAtlases/LungAtlas.aspx

* PTV margin can be decreased by immobilization, motion management, and IGRT techniques.通过制动（固定）、运动管理和影像学引导放疗（IGRT）技术可以缩小计划靶区（PTV）边界。

* Consistent delineation of normal structures is critical for evaluating plans for safety. The RTOG consensus lung-contouring atlas is a useful resource. http://www.rtog.org/CoreLab/ContouringAtlases/LungAtlas.aspx正常结构轮廓勾画的一致性是评估计划安全性的关键。（美国）肿瘤放射治疗协作组织（RTOG）共识的肺轮廓勾画图集是一个有用的资源。

* Commonly used prescription doses and normal tissue dose constraints are summarized in Tables 2 through 5. These are based on published experience, ongoing trials, historical data, modeling, and empirical judgment. Useful references include the recent reviews of normal organ dose responses from the QUANTEC project.常用的处方剂量和正常组织剂量的限制，总结于表2至表5。这均基于已发表的经验、正在进行的试验、历史数据、模型以及经验判断。有用的参考资料包括QUANTEC项目最近对正常器官剂量反应的复习评论。

Node-Negative Early-Stage SABR早期淋巴结阴性的立体定向消融放疗

* The high-dose intensity and conformity of SABR require minimizing the PTV.立体定向消融放疗（SABR）的高剂量强度和适形性要求计划靶区（PTV）降至最小。

* For SABR, intensive regimens of BED ≥100 Gy are associated with significantly better local control and survival than less intensive regimens. In the United States, only regimens of ≤5 fractions meet the arbitrary billing code definition of SBRT, but slightly more protracted regimens are appropriate as well. For centrally located tumors (defined variably as within 2 cm of the proximal bronchial tree and/or abutting mediastinal pleura) and even ultra-central tumors (defined as abutting the proximal bronchial tree), 4 to 10 fraction risk-adapted SABR regimens appear to be effective and safe, while 54 to 60 Gy in 3 fractions is unsafe and should be avoided. The maximum tolerated dose for 5-fraction regimens was studied prospectively in RTOG 0813, preliminary results demonstrate no high-grade toxicities at 50 Gy in 5 fractions.对于立体定向消融放疗（SABR），与非强化方案相比，生物学等效剂量（BED）≥100Gy的强化方案具有更好的局部控制和生存。在美国，只有分割≤5的方案才能符合立体定向放疗任意计费代码的定义，但是，时间更长的方案也略微更合适。对于中心型肿瘤（定义变为近端支气管树和/或邻接纵隔胸膜2cm内）甚至超中心型肿瘤（定义为紧邻支气管树），4-10分割风险调整的立体定向消融方案似乎是安全有效的，而54-60Gy/3f是不安全的，应该避免。RTOG 0813前瞻性研究了5分割方案的最大耐受剂量，初步结果显示50 Gy/5f没有高级别的毒性。

* SABR is most commonly used for tumors up to 5 cm in size, though selected larger isolated tumors can be treated safely if normal tissue constraints are respected.立体定向消融放疗（SABR）最常用于最大5cm的肿瘤，而选择性更大的孤立性肿瘤如果保证正常组织的限制剂量可以安全地治疗。

* Prescription doses incompletely describe the actual delivered doses, which also strongly depend on how the dose is prescribed (to the isocenter vs. an isodose volume covering a proportion of the PTV), the degree of dose heterogeneity, whether tissue density heterogeneity corrections are used, and the type of dose calculation algorithm. All of these must be considered when interpreting or emulating regimens from prior studies.处方剂量不能完全说明实际给予的剂量，在很大程度上还取决于处方剂量如何（等中心与等剂量体积覆盖PTV的比例）、剂量不均的程度、是否使用组织密度不均校正以及剂量算法的类型。当理解或仿效既往研究方案时，必须考虑所有这些因素。

Locally Advanced Stage/Conventionally Fractionated RT局部晚期/常规分割放疗

* IFI omitting ENI allows tumor dose escalation and is associated with a low risk of isolated nodal relapse, particularly in PET/CT–staged patients. Two randomized trials found improved survival for IFI versus ENI, possibly because it enabled dose escalation. IFI is reasonable in order to optimize definitive dosing to the tumor.累及野照射（IFI）而非选择性淋巴结照射（ENI）允许增加肿瘤剂量并可降低单独淋巴结复发风险，特别是在PET/CT分期的患者中。两项随机试验发现，与选择性淋巴结照射（ENI）相比，累及野照射（IFI）改善了生存，可能是因为其能够剂量递增。为了使肿瘤根治量最优化，累及野照射（IFI）是合理的。

* The most commonly prescribed doses for definitive RT are 60 to 70 Gy in 2 Gy fractions. Doses of at least 60 Gy should be given. Dose escalation in RT alone, sequential chemo/RT, or concurrent chemo/RT is associated with better survival in non-randomized comparisons. 根治性放疗最常用的处方剂量是60-70Gy，2Gy/f。应给予至少60Gy的剂量。在非随机对照中，单纯增加放疗剂量、序贯化/放疗或同步化/放疗具有更好的生存。

While optimal RT dose intensification remains a valid question, higher doses of 74 Gy are not currently recommended for routine use.尽管最佳的放疗剂量强度仍然是一个悬而未决的问题，但是，目前不推荐常规使用74Gy的更高剂量。

A meta-analysis demonstrated improved survival with accelerated fractionation RT regimens, and individualized accelerated RT dose intensification is now being evaluated in a randomized trial (RTOG 1106). 一项meta分析显示，加速分割放疗方案和个体化强化加速放疗剂量改善生存，目前正在一项随机试验（RTOG 1106）中评估。

* Doses of 45 to 54 Gy in 1.8 to 2 Gy fractions are standard preoperative doses. Definitive RT doses delivered as preoperative chemoRT can safely be administered and achieve promising nodal clearance and survival rates, but require experience in thoracic surgical techniques to minimize the risk of surgical complications after high-dose RT.

45-54Gy，1.8-2Gy/f是标准的术前剂量。术前化放疗可安全地给予根治性放疗剂量，并可获得极佳的淋巴结清除率和生存率，但是在高剂量放疗后，需要有胸部手术技巧经验以使手术并发症风险将至最低。

* In PORT, the CTV includes the bronchial stump and high-risk draining lymph node stations. Standard doses after complete resection are 50 to 54 Gy in 1.8 to 2 Gy fractions, but a boost may be administered to high-risk regions including areas of nodal extracapsular extension or microscopic positive margins. Lung dose constraints should be more conservative as tolerance appears to be reduced after surgery. 在术后放疗（PORT）中，临床靶体积（CTV）包括支气管残端及高危引流淋巴结区。完全切除术后的标准剂量是50-54Gy，1.8-2Gy/f，但对于高危区域包括淋巴结囊外扩散区域或镜下切缘阳性区域可给予推量照射。肺剂量限制应该更加谨慎，因为术后耐受性似乎降低。

The ongoing European LungART trial provides useful guidelines for PORT technique.正在进行的欧洲肺ART试验为术后放疗（PORT）技术提供了有用的指南。

Advanced Stage/Palliative RT晚期/姑息性放疗

* The dose and fractionation of palliative RT should be individualized based on goals of care, symptoms, performance status, and logistical considerations. Shorter courses of RT provide similar pain relief as longer courses, but with a higher potential need for retreatment, and are preferred for patients with poor performance status and/or shorter life expectancy. For palliation of thoracic symptoms, higher dose/longer-course thoracic RT (eg, ≥30 Gy in 10 fractions) is associated with modestly improved survival and symptoms, particularly in patients with good performance status. When higher doses (>30 Gy) are warranted, technologies to reduce normal tissue irradiation (at least 3D-CRT and including IMRT or proton therapy as appropriate) should be used.姑息性放疗的剂量与分割应根据治疗的目标、症状、一般情况和后勤方面的考量进行个体化治疗。较短程放疗与较长程放疗疼痛缓解相似，但更可能需要再治疗，因此，对于一般情况差和/或预期寿命较短的患者是首选。为了缓解胸部症状，较高剂量/较长疗程的胸部放疗（如≥30Gy/10f）可适当改善生存和症状，尤其是在一般情况良好的患者中。当准许使用更高剂量（> 30 Gy）时，应该使用技术减少正常组织的照射（至少三维适形放疗以及包括调强放疗或酌情使用质子治疗）。

Radiation Therapy Simulation, Planning, and Delivery放射治疗模拟、计划和交付

* Simulation should be performed using CT scans obtained in the RT treatment position with appropriate immobilization devices. IV contrast with or without oral contrast is recommended for better target/organ delineation whenever possible in patients with central tumors or nodal disease. Because IV contrast can affect tissue heterogeneity correction calculations, density masking or use of a pre-contrast scan may be needed when intense enhancement is present.应使用适当固定设备在放疗位置获得的CT扫描进行模拟。在中心型肿瘤或淋巴结病变的患者中，为更好地勾画靶/器官，建议静脉造影±口服对比剂。由于静脉造影可以影响组织的非均匀性校正计算，因此，当进行强烈增强时，可能需要密度蒙罩或使用增强前扫描。

* PET/CT significantly improves targeting accuracy, especially for patients with significant atelectasis and when IV CT contrast is contraindicated. A randomized trial of PET/CT versus CT-only RT planning demonstrated improved preemption of futile radical RT, decreased recurrences, and a trend toward improved overall survival with PET/CT RT planning. Given the potential for rapid progression of NSCLC, PET/CT should be obtained preferably within 4 weeks before treatment. It is ideal to obtain PET/CT in the treatment position. PET/CT明显提高靶区准确性，尤其是对于显著肺不张和有静脉强化CT禁忌症的患者。一项对比PET/CT与单纯CT制定放疗计划的随机试验证明，PET/CT放疗计划可增加排除徒劳无效的根治性放疗、减少复发并且有改善总生存的趋势。考虑到非小细胞肺癌的快速发展潜力，应最好在治疗前4周内获得PET/CT。理想情况下，获得治疗位置的PET/CT。

* Tumor and organ motion, especially owing to breathing, should be assessed or accounted for at simulation. Options include fluoroscopy, inhale/exhale or slow scan CT, or, ideally, 4D-CT. 肿瘤和器官的移动，尤其是由于呼吸所致的移动，在模拟时对其应进行评估或计算在内。选择方案包括透视、吸气/呼气或慢扫描CT，或者，最理想的是4D-CT。

* Photon beam energy should be individualized based on the anatomic location of the tumors and beam paths. In general, photon energies between 4 to 10 MV are recommended for beams passing through low-density lung tissue before entering the tumor. When there is no air gap before the beam enters the tumor (such as for some large mediastinal tumors or tumors attached to the chest wall), higher energies may improve the dose distribution, especially when using a smaller number of fixed beam angles.光子束能量应根据肿瘤的解剖学部位和光子束路径个体化。通常情况下，对于光子束在进入肿瘤之前通过低密度肺组织的情况，建议光子能量在4-10MV之间。当光子束进入肿瘤之前没有空气间隙（如，对于某些大纵隔肿瘤或肿瘤贴于胸壁）时，更高的能量可改善剂量分布，尤其是当使用一个较小的固定束角时。

* Tissue heterogeneity correction and accurate dose calculation algorithms that account for buildup and lateral electron scatter effects in heterogeneous density tissues are recommended. Heterogeneity correction with simple pencil beam algorithms is not recommended.由于横向电子散射作用的积累，因此建议在密度不均匀组织中采用组织不均质的校正和精确的剂量计算方法。不推荐用简单的笔形束算法进行异质性校正。

* Respiratory motion should be managed when motion is excessive. This includes (but is not limited to) forced shallow breathing with abdominal compression, accelerator beam gating with the respiratory cycle, dynamic tumor tracking, active breathing control (ABC), or coaching/biofeedback techniques. If motion is minimal or the ITV is small, motion-encompassing targeting is appropriate. A useful resource for implementation of respiratory motion management is the report of AAPM Task Group 76.当运动过度时，应控制呼吸运动。这包括（但不限于）腹部压迫强迫浅呼吸、周期性呼吸门控加速器束、肿瘤动态跟踪，主动呼吸控制（ABC）或指导/生物反馈技术。如果运动极小或靶区运动范围（ITV）小，包含移动靶区是合适的。美国医学物理学家协会（AAPM）工作组的76报告对呼吸运动管理的实施是有用的资源。

* IGRT—including (but not limited to) orthogonal pair planar imaging and volumetric imaging (such as CBCT or CT on rails)—is recommended when using SABR and 3D-CRT/IMRT with steep dose gradients around the target, when OARs are in close proximity to high-dose regions, and when using complex motion management techniques.当使用立体定向消融放疗（SABR）和3D-CRT/IMRT（三维适形放疗/调强放疗）靶区周围具有陡峭的剂量梯度时，当危险器官（OARs）非常接近高剂量区域时，以及当使用复杂的运动管理技术时，推荐使用影像引导放射治疗技术（IGRT）——包括（但不限于）正交双平面成像和容积成像（如锥形束CT[CBCT]或在轨CT）。

Table 1. Commonly Used Abbreviations in Radiation Therapy放射治疗中常用的缩写

Table 2. Commonly Used Doses for SABR立体定向消融放疗常用剂量

Table 3. Maximum Dose Constraints for SABR立体定向消融放疗的最大剂量限制

Table 4. Commonly Used Doses for Conventionally Fractionated and Palliative RT常规分割和姑息放疗的常用剂量

Table 5. Normal Tissue Dose-Volume Constraints for Conventionally Fractionated RT常规分割放疗正常组织的剂量-体积限制

V xx = % of the whole OAR receiving ≥xx Gy.

V xx = 全部危及器官接受≥xx Gy的百分比。

RTOG 0617 data suggest that even lower radiation doses to the heart than previously appreciated may be detrimental to survival after thoracic RT, and more stringent constraints may be appropriate.

RTOG 0617数据表明，在胸部放疗后，即使比以前更低的心脏照射剂量也可能不利于生存，因此，更严格的限制可能是合适的。

Figure 1. ICRU Report 62 Schema of Target Volume Definitions国际辐射单位与测量委员会62报告的肿瘤靶区定义模式

请注意—表2-5提供的通常或在过去临床试验中的剂量和使用限制为有用的参考，而不是具体的推荐。