DataSheet_1_Radiotherapy Response Assessment of Multiple Myeloma: A Dual-Energy CT Approach With Virtual Non-Calcium Images.docx

BackgroundLife expectancy of patients with multiple myeloma (MM) has increased over the past decades, underlining the importance of local tumor control and avoidance of dose-dependent side effects of palliative radiotherapy (RT). Virtual noncalcium (VNCa) imaging from dual-energy computed tomography (DECT) has been suggested to estimate cellularity and metabolic activity of lytic bone lesions (LBLs) in MM.
ObjectiveTo explore the feasibility of RT response monitoring with DECT-derived VNCa attenuation measurements in MM.
MethodsThirty-three patients with 85 LBLs that had been irradiated and 85 paired non-irradiated LBLs from the same patients were included in this retrospective study. Irradiated and non-irradiated LBLs were measured by circular regions of interest (ROIs) on conventional and VNCa images in a total of 216 follow-up measurements (48 before and 168 after RT). Follow-ups were rated as therapy response, stable disease, or local progression according to the MD Anderson criteria. Receiver operating characteristic (ROC) analysis was performed to discriminate irradiated vs. non-irradiated and locally progressive vs. stable/responsive LBLs using absolute attenuation post-irradiation and percentage attenuation change for patients with pre-irradiation DECT, if available.
ResultsAttenuation of LBLs decreased after RT depending on the time that had passed after irradiation [absolute thresholds for identification of irradiated LBLs 30.5–70.0 HU [best area under the curve [AUC] 0.75 (0.59–0.91)] and -77.0 to -22.5 HU [best AUC 0.85 (0.65–1.00)]/-50% and -117% to -167% proportional change of attenuation on conventional and VNCa images, respectively]. VNCa CT was significantly superior for identification of RT effects in LBLs with higher calcium content [best VNCa AUC 0.96 (0.91–1.00), best conventional CT AUC 0.64 (0.45–0.83)]. Thresholds for early identification of local irradiation failure were >20.5 HU on conventional CT [AUC 0.78 (0.68–0.88)] and >-27 HU on VNCa CT [AUC 0.83 (0.70–0.96)].
ConclusionTherapy response of LBLs after RT can be monitored by VNCa imaging based on regular myeloma scans, which yields potential for optimizing the lesion-specific radiation dose for local tumor control. Decreasing attenuation indicates RT response, while above threshold attenuation of LBLs precedes local irradiation failure.

【背景】近数十年来，多发性骨髓瘤（multiple myeloma, MM）患者的预期寿命有所延长，这凸显了局部肿瘤控制以及规避姑息性放射治疗（radiotherapy, RT）剂量依赖性不良反应的重要性。有研究提出，采用双能计算机断层扫描（dual-energy computed tomography, DECT）获取的虚拟无钙（virtual noncalcium, VNCa）成像，可用于评估MM患者溶骨性骨病变（lytic bone lesions, LBLs）的细胞活性与代谢活跃度。
【目的】本研究旨在探索利用DECT衍生的VNCa衰减值测量，对MM患者的放射治疗应答进行监测的可行性。
【方法】本回顾性研究共纳入33例患者，包含85处经放射治疗的溶骨性骨病变，以及来自同一患者的85处配对未照射溶骨性骨病变。研究采用圆形感兴趣区（regions of interest, ROIs），分别在常规影像与VNCa影像上对照射与未照射的溶骨性骨病变进行测量，共计完成216次随访评估（其中放疗前48次，放疗后168次）。根据MD安德森标准，将随访结果分为治疗应答、疾病稳定或局部进展。对于有放疗前DECT数据的患者，本研究采用放疗后绝对衰减值以及衰减百分比变化量，通过受试者工作特征（receiver operating characteristic, ROC）分析区分照射与未照射病变，以及局部进展与稳定/应答病变。
【结果】溶骨性骨病变的衰减值在放疗后会随放疗后时长发生变化：在常规影像与VNCa影像上，识别照射后病变的最佳绝对阈值分别为30.5~70.0 HU[最佳曲线下面积（area under the curve, AUC）=0.75（0.59~0.91）]与-77.0~-22.5 HU[最佳AUC=0.85（0.65~1.00）]，对应的最佳衰减百分比变化量分别为-50%与-117%~-167%。对于钙含量较高的溶骨性骨病变，VNCa CT在识别放疗效应方面显著优于常规CT[VNCa最佳AUC=0.96（0.91~1.00），常规CT最佳AUC=0.64（0.45~0.83）]。早期识别局部放疗失败的阈值为：常规CT>20.5 HU[AUC=0.78（0.68~0.88）]，VNCa CT>-27 HU[AUC=0.83（0.70~0.96）]。
【结论】基于常规骨髓瘤扫描的VNCa成像可用于监测溶骨性骨病变的放疗应答，这为优化针对病变的放射剂量以实现局部肿瘤控制提供了可能。衰减值降低提示放疗应答，而溶骨性骨病变的衰减值高于阈值则预示着局部放疗失败。