Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University School of Medicine, Baltimore, MD 21231, USA.
Med Phys. 2012 Oct;39(10):6420-30. doi: 10.1118/1.4754653.
Radiation treatment modalities will continue to emerge that promise better clinical outcomes albeit technologically challenging to implement. An important question facing the radiotherapy community then is the need to justify the added technological effort for the clinical return. Mobile tumor radiotherapy is a typical example, where 4D tumor tracking radiotherapy (4DTRT) has been proposed over the simpler conventional modality for better results. The modality choice per patient can depend on a wide variety of factors. In this work, we studied the complication-free tumor control probability (P(+)) index, which combines the physical complexity of the treatment plan with the radiobiological characteristics of the clinical case at hand and therefore found to be useful in evaluating different treatment techniques and estimating the expected clinical effectiveness of different radiation modalities.
4DCT volumes of 18 previously treated lung cancer patients with tumor motion and size ranging from 2 mm to 15 mm and from 4 cc to 462 cc, respectively, were used. For each patient, 4D treatment plans were generated to extract the 4D dose distributions, which were subsequently used with clinically derived radiobiological parameters to compute the P(+) index per modality.
The authors observed, on average, a statistically significant increase in P(+) of 3.4% ± 3.8% (p < 0.003) in favor of 4DTRT. There was high variability among the patients with a <0.5% up to 13.4% improvement in P(+).
The observed variability in the improvement of the clinical effectiveness suggests that the relative benefit of tracking should be evaluated on a per patient basis. Most importantly, this variability could be effectively captured in the computed P(+). The index can thus be useful to discriminate and hence point out the need for a complex modality like 4DTRT over another. Besides tumor mobility, a wide range of other factors, e.g., size, location, fractionation, etc., can affect the relative benefits. Application of the P(+) objective is a simple and effective way to combine these factors in the evaluation of a treatment plan.
尽管实施起来具有技术挑战性，但仍会出现承诺更好临床结果的放射治疗方式。然后，放射治疗界面临的一个重要问题是需要为临床回报证明增加技术投入的合理性。移动肿瘤放射治疗就是一个典型的例子，其中提出了 4D 肿瘤跟踪放射治疗（4DTRT）以取代更简单的常规模式以获得更好的效果。每位患者的模式选择可能取决于各种因素。在这项工作中，我们研究了无并发症肿瘤控制概率（P(+)）指数，该指数将治疗计划的物理复杂性与手头临床病例的放射生物学特征结合在一起，因此被发现可用于评估不同的治疗技术并估计不同放射治疗方式的预期临床效果。
使用 18 位先前接受过治疗的肺癌患者的 4DCT 体积，肿瘤运动范围从 2 毫米到 15 毫米，肿瘤大小从 4 立方厘米到 462 立方厘米不等。为每位患者生成 4D 治疗计划以提取 4D 剂量分布，随后使用临床得出的放射生物学参数计算每种模式的 P(+)指数。
作者观察到，4DTRT 的平均 P(+)提高了 3.4%±3.8%（p<0.003），具有统计学意义。患者之间的变化很大，P(+)的改善幅度从<0.5%到 13.4%不等。
临床效果提高的可变性表明，应根据每位患者评估跟踪的相对益处。最重要的是，在计算出的 P(+)中可以有效地捕捉到这种可变性。因此，该指数可用于区分，从而指出需要像 4DTRT 这样的复杂模式而不是其他模式。除了肿瘤运动性之外，还有广泛的其他因素，例如大小、位置、分割等，会影响相对益处。应用 P(+)目标是在评估治疗计划时将这些因素结合起来的简单而有效的方法。
