From the Preclinical Molecular Imaging, AIT Austrian Institute of Technology GmbH, Seibersdorf.
Division of Nuclear Medicine.
Clin Nucl Med. 2020 Sep;45(9):661-667. doi: 10.1097/RLU.0000000000003157.
Dose response of 22 patients experiencing mCRPC (metastatic castration-resistant prostate cancer) to Lu-PSMA I&T radionuclide therapy was investigated. Dosimetry calculations are used to assess correlations between dosimetric quantities and biomarker values.
The patients' age range was 74 ± 7 years at the time of the investigated treatment cycle, and the mean injected activity was 7416 ± 218 MBq. Planar images at several time points postinjection were used for evaluation of absorbed doses to organs and lesion. Ga-PSMA PET/CT follow-up imaging enabled the determination of individual tumor molecular volume (TMV) shrinkage. Changes in 7 different biomarkers after the first treatment cycle were correlated with the calculated absorbed organ and TMV doses, resulting in a total number of 259 investigated correlations.
Sixty-three TMVs were identified in the bone, lymph node, and liver tissue with an average reduction of 32.3%, 84.7%, and 72.9%, respectively. Absorbed doses per unit of administered activity for organs and lesions show good agreement with previous works (0.77, 0.71, and 0.27 mGy/MBq for parotid gland, kidneys, and liver as well as 4.38, 5.47, and 4.95 mGy/MBq for bone, lymph node, and liver malignancies, respectively). Only 37 of 259 possible correlations turned out to be statistically significant, 26 of which are associated with the absorbed dose of an organ and the decrease of alkaline phosphatases.
Although treatment with Lu-PSMA I&T leads to a big reduction of TMV in patients with mCRPC, the lack of correlations calls for studies using voxel-wise dosimetry based on SPECT/CTs.
研究 22 例转移性去势抵抗性前列腺癌（mCRPC）患者接受 Lu-PSMA I&T 放射性核素治疗的剂量反应。通过剂量计算评估剂量学参数与生物标志物值之间的相关性。
在接受研究性治疗周期时，患者的年龄范围为 74 ± 7 岁，平均注射活度为 7416 ± 218 MBq。注射后多个时间点的平面图像用于评估器官和病变的吸收剂量。Ga-PSMA PET/CT 随访成像可确定个体肿瘤分子体积（TMV）缩小。首次治疗周期后 7 种不同生物标志物的变化与计算出的吸收器官和 TMV 剂量相关，共进行了 259 次相关性研究。
在骨、淋巴结和肝脏组织中确定了 63 个 TMV，平均分别减少了 32.3%、84.7%和 72.9%。单位放射性活度的器官和病变吸收剂量与之前的研究结果吻合较好（腮腺、肾脏和肝脏分别为 0.77、0.71 和 0.27 mGy/MBq，骨、淋巴结和肝脏恶性肿瘤分别为 4.38、5.47 和 4.95 mGy/MBq）。在 259 个可能的相关性中，只有 37 个具有统计学意义，其中 26 个与器官吸收剂量和碱性磷酸酶降低相关。
尽管 Lu-PSMA I&T 治疗可导致 mCRPC 患者的 TMV 明显减少，但相关性缺乏表明需要进行基于 SPECT/CT 的体素剂量学研究。
