University Medical Imaging Toronto, University Health Network, Sinai Health Systems, Women's College Hospital, University of Toronto, Toronto, ON M5G 2N2, Canada.
Department of Surgery, University Health Network, Toronto, ON M5G 2C4, Canada.
Tomography. 2024 Aug 30;10(9):1354-1364. doi: 10.3390/tomography10090102.
Tumor hypoxia is a negative prognostic factor in many tumors and is predictive of metastatic spread and poor responsiveness to both chemotherapy and radiotherapy. To assess the feasibility of using F-Fluoroazomycin arabinoside (FAZA) PET/MR to image tumor hypoxia in patients with locally advanced rectal cancer (LARC) prior to and following neoadjuvant chemoradiotherapy (nCRT). The secondary objective was to compare different reference tissues and thresholds for tumor hypoxia quantification. Eight patients with histologically proven LARC were included. All patients underwent F-FAZA PET/MR prior to initiation of nCRT, four of whom also had a second scan following completion of nCRT and prior to surgery. Tumors were segmented using T-weighted MR. Each voxel within the segmented tumor was defined as hypoxic or oxic using thresholds derived from various references: ×1.0 or ×1.2 SUVmean of blood pool [BP] or left ventricle [LV] and SUVmean +3SD for gluteus maximus. Correlation coefficient (CoC) between HF and tumor SUVmax/reference SUVmean TRR for the various thresholds was calculated. Hypoxic fraction (HF), defined as the % hypoxic voxels within the tumor volume was calculated for each reference/threshold. For all cases, baseline and follow-up, the CoCs for gluteus maximus and for BP and LV (×1.0) were 0.241, 0.344, and 0.499, respectively, and HFs were (median; range) 16.6% (2.4-33.8), 36.8% (0.3-72.9), and 30.7% (0.8-55.5), respectively. For a threshold of ×1.2, the CoCs for BP and LV as references were 0.611 and 0.838, respectively, and HFs were (median; range) 10.4% (0-47.6), and 4.3% (0-20.1%), respectively. The change in HF following nCRT ranged from (-18.9%) to (+54%). Imaging of hypoxia in LARC with F-FAZA PET/MR is feasible. Blood pool as measured in the LV appears to be the most reliable reference for calculating the HF. There is a wide range of HF and variable change in HF before and after nCRT.
肿瘤缺氧是许多肿瘤的负预后因素，与转移扩散和对化疗和放疗的低反应性相关。本研究旨在评估氟代阿霉素阿拉伯呋喃糖苷（FAZA）PET/MR 用于在接受新辅助放化疗（nCRT）前后成像局部晚期直肠癌（LARC）患者肿瘤缺氧的可行性。次要目标是比较不同参考组织和肿瘤缺氧定量的阈值。
纳入了 8 例经组织学证实的 LARC 患者。所有患者在 nCRT 前进行 F-FAZA PET/MR 检查，其中 4 例患者在 nCRT 完成后和手术前进行了第二次扫描。使用 T 加权磁共振（MR）对肿瘤进行分割。使用来自各种参考值的阈值（血池 [BP] 或左心室 [LV] 的×1.0 或 SUVmean 和臀肌的 SUVmean +3SD），对分割的肿瘤内的每个体素定义为缺氧或氧合。计算了各种阈值下 HF 和肿瘤 SUVmax/参考 SUVmean TRR 之间的相关系数（CoC）。为每个参考/阈值计算肿瘤体积内的缺氧分数（HF），定义为缺氧体素的百分比。
对于所有病例（基线和随访），臀肌和 BP 和 LV（×1.0）的 CoC 分别为 0.241、0.344 和 0.499，HF 分别为（中位数；范围）16.6%（2.4-33.8）、36.8%（0.3-72.9）和 30.7%（0.8-55.5）。对于阈值为×1.2，BP 和 LV 作为参考的 CoC 分别为 0.611 和 0.838，HF 分别为（中位数；范围）10.4%（0-47.6）和 4.3%（0-20.1%）。nCRT 后 HF 的变化范围为（-18.9%）至（+54%）。
用 F-FAZA PET/MR 对 LARC 进行缺氧成像具有可行性。LV 中测量的血池似乎是计算 HF 的最可靠参考。在 nCRT 前后，HF 的范围很广，HF 的变化也不同。
