University of Cambridge Department of Oncology, Oncology Centre, Addenbrookes Hospital, Cambridge, UK.
Br J Radiol. 2012 Sep;85(1017):1263-71. doi: 10.1259/bjr/27924223. Epub 2012 Feb 14.
To estimate the benefit of introduction of image-guided radiotherapy (IGRT) to prostate radiotherapy practice with current clinical target volume-planning target volume (PTV) margins of 5-10 mm.
Systematic error data collected from 50 patients were used together with a random error of σ=3.0 mm to model non-IGRT treatment. IGRT was modelled with residual errors of Σ=σ=1.5 mm. Population tumour control probability (TCP(pop)) was calculated for two three-dimensional conformal radiotherapy techniques: two-phase and concomitant boost. Treatment volumes and dose prescriptions were ostensibly the same. The relative field sizes of the treatment techniques, distribution of systematic errors and correlations between movement axes were examined.
The differences in TCP(pop) between the IGRT and non-IGRT regimes were 0.3% for the two-phase and 1.5% for the concomitant boost techniques. A 2-phase plan, in each phase of which the 95% isodose conformed to its respective PTV, required fields that were 3.5 mm larger than those required for the concomitant boost plan. Despite the larger field sizes, the TCP (without IGRT) in the two-phase plan was only 1.7% higher than the TCP in the concomitant boost plan. The deviation of craniocaudal systematic errors (p=0.02) from a normal distribution, and the correlation of translations in the craniocaudal and anteroposterior directions (p<0.0001) were statistically significant.
The expected population benefit of IGRT for the modelled situation was too small to be detected by a clinical trial of reasonable size, although there was a significant benefit to individual patients. For IGRT to have an observable population benefit, the trial would need to use smaller margins than those used in this study. Concomitant treatment techniques permit smaller fields and tighter conformality than two phases planned separately.
评估在当前临床靶区-计划靶区（PTV）边界为 5-10mm 的前列腺放射治疗中引入图像引导放射治疗（IGRT）的获益。
使用从 50 名患者中收集的系统误差数据，结合 3.0mm 的随机误差 σ，对非 IGRT 治疗进行建模。IGRT 采用残余误差 Σ=σ=1.5mm 进行建模。针对两种三维适形放射治疗技术（两阶段和同期加量）计算了群体肿瘤控制概率（TCP（pop））。治疗体积和剂量处方表面上是相同的。检查了治疗技术的相对射野大小、系统误差分布和运动轴之间的相关性。
IGRT 和非 IGRT 方案之间 TCP（pop）的差异分别为两阶段方案的 0.3%和同期加量方案的 1.5%。在两阶段方案中，每个阶段的 95%等剂量线均符合其相应的 PTV，所需射野比同期加量方案大 3.5mm。尽管射野较大，但两阶段方案中的 TCP（无 IGRT）仅比同期加量方案高 1.7%。头脚向系统误差的偏离（p=0.02）不符合正态分布，以及头脚向和前后向平移之间的相关性（p<0.0001）具有统计学意义。
在该模型情况下，IGRT 的预期人群获益太小，无法通过合理规模的临床试验检测到，尽管对个别患者有明显的获益。为了使 IGRT 具有可观察到的人群获益，试验需要使用比本研究中小的边界。同期治疗技术比两阶段分别计划的治疗技术允许更小的射野和更紧密的适形性。
