a Medical Radiation Physics, Department of Physics , Stockholm University , Stockholm , Sweden.
b The Skandion Clinic , Uppsala , Sweden.
Acta Oncol. 2018 Apr;57(4):485-490. doi: 10.1080/0284186X.2017.1400177. Epub 2017 Nov 16.
Tumour hypoxia is associated with increased radioresistance and poor response to radiotherapy. Pre-treatment assessment of tumour oxygenation could therefore give the possibility to tailor the treatment by calculating the required boost dose needed to overcome the increased radioresistance in hypoxic tumours. This study concerned the derivation of a non-linear conversion function between the uptake of the hypoxia-PET tracer F-HX4 and oxygen partial pressure (pO).
Building on previous experience with FMISO including experimental data on tracer uptake and pO, tracer-specific model parameters were derived for converting the normalised HX4-uptake at the optimal imaging time point to pO. The conversion function was implemented in a Python-based computational platform utilising the scripting and the registration modules of the treatment planning system RayStation. Subsequently, the conversion function was applied to determine the pO in eight non-small-cell lung cancer (NSCLC) patients imaged with HX4-PET before the start of radiotherapy. Automatic segmentation of hypoxic target volumes (HTVs) was then performed using thresholds around 10 mmHg. The HTVs were compared to sub-volumes segmented based on a tumour-to-blood ratio (TBR) of 1.4 using the aortic arch as the reference oxygenated region. The boost dose required to achieve 95% local control was then calculated based on the calibrated levels of hypoxia, assuming inter-fraction reoxygenation due to changes in acute hypoxia but no overall improvement of the oxygenation status.
Using the developed conversion tool, HTVs could be obtained using pO a threshold of 10 mmHg which were in agreement with the TBR segmentation. The dose levels required to the HTVs to achieve local control were feasible, being around 70-80 Gy in 24 fractions.
Non-linear conversion of tracer uptake to pO in NSCLC imaged with HX4-PET allows a quantitative determination of the dose-boost needed to achieve a high probability of local control.
肿瘤缺氧与放射抵抗增加和对放射治疗反应不良有关。因此，通过计算克服缺氧肿瘤放射抵抗所需的额外剂量，对肿瘤氧合状态进行治疗前评估，可以提供针对治疗的可能性。本研究旨在建立 F-HX4 摄取与氧分压（pO）之间的非线性转换函数。
基于 FMISO 的先前经验，包括示踪剂摄取和 pO 的实验数据，为将最佳成像时间点的归一化 HX4 摄取转换为 pO ，推导了示踪剂特异性模型参数。转换函数在一个基于 Python 的计算平台中实现，该平台利用了治疗计划系统 RayStation 的脚本和注册模块。随后，该转换函数应用于在开始放射治疗前用 HX4-PET 成像的 8 例非小细胞肺癌（NSCLC）患者，以确定 pO。然后，使用 10mmHg 左右的阈值自动分割缺氧靶区（HTV）。将 HTV 与基于主动脉弓作为参考氧合区域的 1.4 肿瘤/血液比（TBR）分割的亚体积进行比较。假设由于急性缺氧变化导致分次间再氧合，但整体氧合状态没有改善，然后根据校准的缺氧水平计算实现 95%局部控制所需的提升剂量。
使用开发的转换工具，可以使用 pO 为 10mmHg 的阈值获得 HTV，这与 TBR 分割结果一致。HTV 实现局部控制所需的剂量水平是可行的，在 24 分次中约为 70-80Gy。
在接受 HX4-PET 成像的 NSCLC 中，示踪剂摄取到 pO 的非线性转换允许定量确定实现高局部控制概率所需的剂量提升。
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