McWilliam Alan, Dootson Chloe, Graham Lewis, Banfill Kathryn, Abravan Azadeh, van Herk Marcel
Division of Clinical Cancer Science, School of Medical Sciences, Faculty of Biology, Medicine and Health, University of Manchester, UK.
Department of Radiotherapy Related Research, The Christie NHS Foundation Trust, Manchester, UK.
Phys Imaging Radiat Oncol. 2020 Jul 30;15:46-51. doi: 10.1016/j.phro.2020.07.002. eCollection 2020 Jul.
For lung cancer patients treated with radiotherapy, radiation dose to the heart has been associated with overall survival, with volumetric dose statistics widely presented. However, critical cardiac structures are present on the hearts surface, where this approach may be sub-optimal. In this work we present a methodology for creating cardiac surface dose maps and identify regions where excess dose is associated with in worse overall survival.
A modified cylindrical coordinate system was implemented to map the cardiac surface dose for lung cancer patients. Validation was performed by mapping the cardiac chambers for 55 patients, fitting a point spread function (PSF) to the blurred edge. To account for this uncertainty, dose maps were blurred by a 2D-Gaussian with width described by the PSF. Permutation testing identified regions where excess dose was associated with worse patient survival. The 99th percentile of the max t-value then defined a cardiac surface region to extract dose, from each patient, to be analysed in a multivariable cox-proportional hazards survival model.
Cardiac surface maps were created for 648 lung cancer patients. Cardiac surface dose maps were blurred with a 2D- Gaussian filter of size σ = 4.3° and σ = 1.3units to account for mapping uncertainties. Permutation testing identified significant differences across the surface of the right atria, p < 0.001, at all timepoints. The median dose to the region defined by the 99th percentile of the maximum t-value was 18.5 Gy. Multivariable analysis showed the dose to this region was significantly associated with survival, hazard ratio 1.01 Gy, p = 0.03, controlling for confounding variables.
Cardiac surface mapping was successfully implemented and identified a region where excess dose was associated with worse patient survival. This region extended over the right atria, potentially suggesting an interaction with the hearts electrical conduction system.
对于接受放射治疗的肺癌患者，心脏所接受的辐射剂量与总生存期相关，容积剂量统计数据也被广泛报道。然而，心脏表面存在关键心脏结构，在此处这种方法可能并非最优。在本研究中，我们提出一种创建心脏表面剂量图的方法，并识别出过量剂量与较差总生存期相关的区域。
采用一种改良的柱面坐标系来绘制肺癌患者的心脏表面剂量。通过对55例患者的心脏腔室进行绘图，并将点扩散函数（PSF）拟合到模糊边缘来进行验证。为了考虑这种不确定性，剂量图用二维高斯模糊，其宽度由PSF描述。置换检验确定了过量剂量与较差患者生存相关的区域。然后，最大t值的第99百分位数定义了一个心脏表面区域，用于从每位患者中提取剂量，以便在多变量Cox比例风险生存模型中进行分析。
为648例肺癌患者创建了心脏表面图。心脏表面剂量图用大小为σ = 4.3°和σ = 1.3单位的二维高斯滤波器进行模糊处理，以考虑绘图不确定性。置换检验在所有时间点均发现右心房表面存在显著差异，p < 0.001。由最大t值的第99百分位数定义的区域的中位剂量为18.5 Gy。多变量分析表明，该区域的剂量与生存显著相关，风险比为1.01 Gy，p = 0.03，同时控制了混杂变量。
成功实施了心脏表面绘图，并识别出一个过量剂量与较差患者生存相关的区域。该区域延伸至右心房，可能提示与心脏电传导系统存在相互作用。
