Robinson M, Muirhead R, McGowan D R, Chu K-Y, Jacobs C, Hawkins M A
Department of Clinical Oncology, Oxford University Hospitals NHS Trust, Oxford, UK; Department of Oncology, University of Oxford, Oxford, UK.
Department of Clinical Oncology, Oxford University Hospitals NHS Trust, Oxford, UK.
Clin Oncol (R Coll Radiol). 2023 Oct;35(10):e622-e627. doi: 10.1016/j.clon.2023.06.001. Epub 2023 Jun 6.
Irradiation of pelvic bone marrow (PBM) at the level of the typical low dose bath of intensity-modulated radiotherapy delivery (10-20 Gy) is associated with an increased risk of haematological toxicity, particularly when combined with concurrent chemotherapy. Although sparing of the whole of the PBM at a 10-20 Gy dose level is unachievable, it is known that PBM is divided into haematopoietically active and inactive regions that are identifiable based on the threshold uptake of [F]-fluorodeoxyglucose (FDG) seen on positron emission tomography-computed tomography (PET-CT). In published studies to date, the definition of active PBM widely used is that of a standardised uptake value (SUV) greater than the mean SUV of the whole PBM prior to the start of chemoradiation. These studies include those looking at developing an atlas-based approach to contouring active PBM. Using baseline and mid-treatment FDG PET scans acquired as part of a prospective clinical trial we sought to determine the suitability of the current definition of active bone marrow as representative of differential underlying cell physiology.
Active and inactive PBM were contoured on baseline PET-CT and using deformable registration mapped onto mid-treatment PET-CT. Volumes were cropped to exclude definitive bone, voxel SUV extracted and the change between scans calculated. Change was compared using Mann-Whitney U testing.
Active and inactive PBM were shown to respond differentially to concurrent chemoradiotherapy. The median absolute response of active PBM for all patients was -0.25 g/ml, whereas the median inactive PBM response was -0.02 g/ml. Significantly, the inactive PBM median absolute response was shown to be near zero with a relatively unskewed distribution (0.12).
These results would support the definition of active PBM as FDG uptake greater than the mean of the whole structure as being representative of underlying cell physiology. This work would support the development of atlas-based approaches published in the literature to contour active PBM based on the current definition as being suitable.
在调强放疗的典型低剂量范围（10 - 20 Gy）对盆腔骨髓（PBM）进行照射与血液学毒性风险增加相关，尤其是与同步化疗联合时。虽然在10 - 20 Gy剂量水平下保全整个PBM是无法实现的，但已知PBM可分为造血活跃区和非活跃区，可根据正电子发射断层扫描 - 计算机断层扫描（PET - CT）上[F] - 氟脱氧葡萄糖（FDG）的阈值摄取来识别。在迄今为止已发表的研究中，广泛使用的活跃PBM的定义是标准化摄取值（SUV）大于放化疗开始前整个PBM的平均SUV。这些研究包括那些着眼于开发基于图谱的方法来勾勒活跃PBM轮廓的研究。利用作为一项前瞻性临床试验一部分获取的基线和治疗中期FDG PET扫描，我们试图确定当前活跃骨髓定义作为潜在细胞生理学差异代表的适用性。
在基线PET - CT上勾勒出活跃和非活跃PBM，并使用可变形配准映射到治疗中期PET - CT上。裁剪体积以排除确定性骨，提取体素SUV并计算扫描之间的变化。使用曼 - 惠特尼U检验比较变化。
活跃和非活跃PBM对同步放化疗的反应不同。所有患者活跃PBM的中位绝对反应为 - 0.25 g/ml，而非活跃PBM的中位反应为 - 0.02 g/ml。值得注意的是，非活跃PBM的中位绝对反应显示接近零，分布相对不偏态（0.12）。
这些结果支持将活跃PBM定义为FDG摄取大于整个结构的平均值，作为潜在细胞生理学的代表。这项工作将支持文献中发表的基于图谱的方法的开发，以根据当前定义勾勒活跃PBM轮廓是合适的。
