Shelley Leila E A, Sutcliffe Michael P F, Thomas Simon J, Noble David J, Romanchikova Marina, Harrison Karl, Bates Amy M, Burnet Neil G, Jena Raj
Cancer Research UK VoxTox Research Group, Cambridge University Hospitals NHS Foundation Trust, Department of Oncology, Addenbrooke's Hospital, Cambridge CB2 0QQ, United Kingdom.
Edinburgh Cancer Centre, Western General Hospital, Edinburgh EH4 2XU, United Kingdom.
Phys Imaging Radiat Oncol. 2020 Apr;14:87-94. doi: 10.1016/j.phro.2020.05.006.
Associations between dose and rectal toxicity in prostate radiotherapy are generally poorly understood. Evaluating spatial dose distributions to the rectal wall (RW) may lead to improvements in dose-toxicity modelling by incorporating geometric information, masked by dose-volume histograms. Furthermore, predictive power may be strengthened by incorporating the effects of interfraction motion into delivered dose calculations.Here we interrogate 3D dose distributions for patients with and without toxicity to identify rectal subregions at risk (SRR), and compare the discriminatory ability of planned and delivered dose.
Daily delivered dose to the rectum was calculated using image guidance scans, and accumulated at the voxel level using biomechanical finite element modelling. SRRs were statistically determined for rectal bleeding, proctitis, faecal incontinence and stool frequency from a training set (n = 139), and tested on a validation set (n = 47).
SRR patterns differed per endpoint. Analysing dose to SRRs improved discriminative ability with respect to the full RW for three of four endpoints. Training set AUC and OR analysis produced stronger toxicity associations from accumulated dose than planned dose. For rectal bleeding in particular, accumulated dose to the SRR (AUC 0.76) improved upon dose-toxicity associations derived from planned dose to the RW (AUC 0.63). However, validation results could not be considered significant.
Voxel-level analysis of dose to the RW revealed SRRs associated with rectal toxicity, suggesting non-homogeneous intra-organ radiosensitivity. Incorporating spatial features of accumulated delivered dose improved dose-toxicity associations. This may be an important tool for adaptive radiotherapy in the future.
前列腺放疗中剂量与直肠毒性之间的关联通常了解甚少。评估直肠壁（RW）的空间剂量分布，通过纳入被剂量体积直方图掩盖的几何信息，可能会改进剂量 - 毒性建模。此外，将分次间运动的影响纳入实际 delivered 剂量计算中，可能会增强预测能力。在此，我们研究有毒性和无毒患者的三维剂量分布，以识别有风险的直肠亚区域（SRR），并比较计划剂量和实际 delivered 剂量的辨别能力。
使用图像引导扫描计算每日直肠 delivered 剂量，并使用生物力学有限元建模在体素水平上进行累积。从训练集（n = 139）中通过统计学方法确定直肠出血、直肠炎、大便失禁和排便频率的 SRR，并在验证集（n = 47）上进行测试。
不同终点的 SRR 模式不同。对于四个终点中的三个，分析 SRR 的剂量相对于整个 RW 提高了辨别能力。训练集的 AUC 和 OR 分析表明，累积剂量比计划剂量产生更强的毒性关联。特别是对于直肠出血，SRR 的累积剂量（AUC 0.76）比从 RW 的计划剂量得出的剂量 - 毒性关联（AUC 0.63）有所改善。然而，验证结果不具有统计学意义。
对 RW 剂量的体素水平分析揭示了与直肠毒性相关的 SRR，表明器官内放射敏感性不均匀。纳入累积 delivered 剂量的空间特征改善了剂量 - 毒性关联。这可能是未来自适应放疗的重要工具。
