Medical Research Council Population Health Research Unit, Nuffield Department of Population Health, University of Oxford, United Kingdom.
Clinical Trial Service Unit, Nuffield Department of Population Health, University of Oxford, United Kingdom.
Pract Radiat Oncol. 2019 May;9(3):158-171. doi: 10.1016/j.prro.2019.01.004. Epub 2019 Jan 26.
Incidental cardiac exposure during radiation therapy may cause heart disease. Dose-response relationships for cardiac structures (segments) may show which ones are most sensitive to radiation. Radiation-related cardiac injury can take years to develop; thus, studies need to involve women treated using 2-dimensional planning, with segment doses estimated using a typical computed tomography (CT) scan. We assessed whether such segment doses are accurate enough to use in dose-response relationships using the radiation therapy charts of women with known segment injury. We estimated interregimen and interpatient segment dose variability and segment dose correlations.
The radiation therapy charts of 470 women with cardiac segment injury after breast cancer radiation therapy were examined, and 41 regimens were identified. Regimens were reconstructed on a typical CT scan. Doses were estimated for 5 left ventricle (LV) and 10 coronary artery segments. Correlations between cardiac segments were estimated. Interpatient dose variation was assessed in 10 randomly selected CT scans for left regimens and in 5 for right regimens.
For the typical CT scan, interregimen segment dose variation was substantial (range, LV segments <1-39 Gy; coronary artery segments <1-48 Gy). In 10 CT scans, interpatient segment dose variation was higher for segments near field borders (range, 3-47 Gy) than other segments (range, <2 Gy). Doses to different left-anterior descending coronary artery (LADCA) segments were highly correlated with each other, as were doses to different LV segments. Also, LADCA segment doses were highly correlated with doses to LV segments usually supplied by the LADCA. For individual regimens there was consistency in hotspot location and segment ranking of higher-versus-lower dose.
The scope for developing quantitative cardiac segment dose-response relationships in patients who had 2-dimensional planning is limited because different segment doses are often highly correlated, and segment-specific dose uncertainties are not independent of each other. However, segment-specific doses may be reliably used to rank segments according to higher-versus-lower doses.
放射治疗过程中偶然的心脏照射可能导致心脏病。心脏结构（节段）的剂量反应关系可能表明哪些节段对辐射最敏感。与辐射相关的心脏损伤可能需要数年才能发展；因此，需要使用二维规划治疗的女性参与研究，使用典型的计算机断层扫描 (CT) 扫描估计节段剂量。我们评估了使用已知节段损伤的女性的放射治疗图表，这些节段剂量是否足够准确用于剂量反应关系。我们估计了不同方案和不同患者的节段剂量变异性和节段剂量相关性。
检查了 470 名乳腺癌放射治疗后心脏节段损伤的女性的放射治疗图表，并确定了 41 种方案。方案在典型 CT 扫描上进行重建。估计了 5 个左心室 (LV) 和 10 个冠状动脉节段的剂量。估计了心脏节段之间的相关性。在 10 个随机选择的左方案和 5 个右方案的 CT 扫描中评估了患者间剂量变化。
对于典型的 CT 扫描，不同方案的节段剂量变化很大（范围，LV 节段<1-39Gy；冠状动脉节段<1-48Gy）。在 10 个 CT 扫描中，近野边界的节段（范围，3-47Gy）的患者间节段剂量变化高于其他节段（范围，<2Gy）。不同左前降支冠状动脉 (LADCA) 节段的剂量彼此高度相关，LV 节段也是如此。此外，LADCA 节段的剂量与通常由 LADCA 供应的 LV 节段的剂量高度相关。对于个别方案，较高剂量与较低剂量的热点位置和节段排名一致。
在二维规划的患者中开发定量心脏节段剂量反应关系的范围有限，因为不同的节段剂量通常高度相关，并且节段特异性剂量不确定性彼此不独立。然而，节段特异性剂量可用于根据较高剂量与较低剂量对节段进行可靠排序。
