Department of Radiology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa
Department of Radiology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa.
J Nucl Med. 2018 Nov;59(11):1692-1698. doi: 10.2967/jnumed.117.202903. Epub 2018 Mar 9.
Pretherapy PET with Y-DOTATOC is considered the ideal dosimetry protocol for Y-DOTATOC therapy; however, its cost, limited availability, and need for infusion of amino acids to mimic the therapy administration limit its use in the clinical setting. The goal of this study was to develop a dosimetric method for Y-DOTATOC using Y-DOTATOC PET/CT and bremsstrahlung SPECT/CT and to determine whether dosimetry-based administered activities differ significantly from standard administered activities. This was a prospective phase 2 trial of Y-DOTATOC therapy in patients with somatostatin receptor-positive tumors. Y-DOTATOC was given in 3 cycles 6-8 wk apart. In the first cycle of therapy, adults received 4.4 GBq and children received 1.85 GBq/m; the subsequent administered activities were adjusted according to the dosimetry of the preceding cycle so as not to exceed a total kidney dose of 23 Gy and bone marrow dose of 2 Gy. The radiation dose to the kidneys was determined from serial imaging sessions consisting of time-of-flight Y-DOTATOC PET/CT at 5 h after therapy and Y-DOTATOC bremsstrahlung SPECT/CT at 6, 24, 48, and 72 h. The PET/CT data were used to measure the absolute concentration of Y-DOTATOC and to calibrate the bremsstrahlung SPECT kidney clearance data. The radiation dose to the kidneys was determined by multiplying the time-integrated activity (from the fitted biexponential curve of renal clearance of Y-DOTATOC) with the energy emitted per decay, divided by the mass of the kidneys. The radiation dose to the kidneys per cycle of Y-DOTATOC therapy was highly variable among patients, ranging from 0.32 to 3.0 mGy/MBq. In 17 (85%) of the 20 adult patients who received the second and the third treatment cycles of Y-DOTATOC, the administered activity was modified by at least 20% from the starting administered activity. Renal dosimetry of Y-DOTATOC is feasible using Y-DOTATOC time-of-flight PET/CT and bremsstrahlung SPECT/CT and has a significant impact on the administered activity in treatment cycles.
治疗前使用 Y-DOTATOC 的正电子发射断层扫描（PET）被认为是 Y-DOTATOC 治疗的理想剂量测定方案；然而，其成本高、可用性有限以及需要输注氨基酸以模拟治疗给药，限制了其在临床环境中的应用。本研究的目的是开发一种使用 Y-DOTATOC PET/CT 和韧致辐射 SPECT/CT 的 Y-DOTATOC 剂量测定方法，并确定基于剂量测定的给药活性是否与标准给药活性有显著差异。这是一项在生长抑素受体阳性肿瘤患者中进行的 Y-DOTATOC 治疗的前瞻性 2 期试验。Y-DOTATOC 每 6-8 周给予 3 个周期。在治疗的第一个周期中，成人患者接受 4.4GBq，儿童患者接受 1.85GBq/m；随后的给药活性根据前一个周期的剂量测定进行调整，以避免肾脏总剂量超过 23Gy 和骨髓剂量超过 2Gy。通过连续的成像过程来确定肾脏的辐射剂量，这些成像过程包括治疗后 5 小时进行的飞行时间 Y-DOTATOC PET/CT 和治疗后 6、24、48 和 72 小时进行的 Y-DOTATOC 韧致辐射 SPECT/CT。PET/CT 数据用于测量 Y-DOTATOC 的绝对浓度并校准韧致辐射 SPECT 肾脏清除数据。肾脏的辐射剂量通过乘以（从 Y-DOTATOC 肾清除拟合的双指数曲线获得的）时间积分活动与每衰减发射的能量，除以肾脏的质量来确定。Y-DOTATOC 治疗周期中每个患者的肾脏辐射剂量差异很大，范围为 0.32 至 3.0mGy/MBq。在接受 Y-DOTATOC 第二次和第三次治疗周期的 20 名成年患者中，有 17 名（85%）患者的给药活性至少从起始给药活性改变了 20%。使用 Y-DOTATOC 飞行时间 PET/CT 和韧致辐射 SPECT/CT 进行 Y-DOTATOC 的肾脏剂量测定是可行的，并且对治疗周期中的给药活性有显著影响。
