Suit Herman
Department of Radiation Oncology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA.
Int J Radiat Oncol Biol Phys. 2002 Jul 15;53(4):798-809. doi: 10.1016/s0360-3016(02)02851-1.
To review the current limits on the efficacy of radiotherapy (RT) due to technical factors and to assess the potential for major improvements in technology.
The method of this review was to assess the efficacy of current RT in general terms; strategies for improving RT; historical record of technological advances; rationale for further reductions of treatment volume; and importance of defining and excluding nontarget tissues from the target volume. The basis for the interest in proton beam RT is developed, and the relative dose distributions of intensity-modulated radiotherapy (IMRT) and intensity-modulated proton RT (IMPT) are discussed. The discovery of the proton and the first proposal that protons be used in RT is described. This is followed by a brief mention of the clinical outcome studies of proton RT. Likely technical advances to be integrated into advanced proton RT are considered, specifically, four-dimensional treatment planning and delivery. Finally, the increment in cost of some of these developments is presented.
For definitive RT, dose limits are set by the tolerance of normal tissues/structures adjacent or near to the target. Using imaging fusion of CT, MRI, positron emission tomography, magnetic resonance spectroscopic imaging, and other studies will result in improved definition of the target margins. Proton beams are likely to replace photon beams because of their physical characteristics. Namely, for each beam path, the dose deep to the target is zero, across the target it is uniform, and proximal to the target it is less. Proton therapy can use as many beams, beam angles, noncoplanar, and dynamic, as well as static, intensity modulation, as can photon plans. The ability for much greater accuracy in defining the target position in space and then maintaining the target in a constant position in the radiation beam despite target movement between and during dose fractions will be possible. The cost of proton RT will be modestly higher than comparable high technology photon therapy.
The technology of RT is clearly experiencing intense and rapid technical developments as pertains to treatment planning and dose delivery. It is predicted that radical dose RT will move to proton beam technology and that the treatment will be four dimensional (the fourth dimension is time). The impact will be higher tumor control probability and reduced frequency and severity of treatment-related morbidity.
回顾由于技术因素导致的放射治疗（RT）疗效的当前限制，并评估技术取得重大进步的潜力。
本综述的方法是从总体上评估当前RT的疗效；改善RT的策略；技术进步的历史记录；进一步缩小治疗体积的基本原理；以及从靶体积中定义和排除非靶组织的重要性。阐述了对质子束RT感兴趣的依据，并讨论了调强放疗（IMRT）和调强质子放疗（IMPT）的相对剂量分布。描述了质子的发现以及首次提出在RT中使用质子的建议。随后简要提及了质子RT的临床结果研究。考虑了可能整合到先进质子RT中的技术进步，特别是四维治疗计划和实施。最后，介绍了其中一些发展的成本增加情况。
对于根治性RT，剂量限制由靶区附近或邻近的正常组织/结构的耐受性设定。使用CT、MRI、正电子发射断层扫描、磁共振波谱成像和其他研究的成像融合将改善靶区边缘的定义。由于质子束的物理特性，它们可能会取代光子束。也就是说，对于每条束路径，靶区深处的剂量为零，穿过靶区时剂量均匀，靶区近端剂量较小。质子治疗可以使用与光子计划一样多的束、束角、非共面、动态以及静态调强。尽管在分次剂量之间和期间靶区会移动，但在空间中更精确地定义靶区位置并随后在辐射束中将靶区保持在恒定位置的能力将成为可能。质子RT的成本将略高于可比的高科技光子治疗。
RT技术在治疗计划和剂量输送方面显然正在经历激烈而迅速的技术发展。预计根治性剂量RT将转向质子束技术，并且治疗将是四维的（第四维是时间）。其影响将是提高肿瘤控制概率，并降低与治疗相关的发病率的频率和严重程度。
