Background: The gastrin-releasing peptide receptor (GRPr) is highly overexpressed in several solid tumors, including treatment-naïve and recurrent prostate cancer. [68Ga]Ga-RM2 is a well-established radiotracer for PET imaging of GRPr, and [177Lu]Lu-RM2 has been proposed as a therapeutic alternative for patients with heterogeneous and/or low expression of PSMA. In this study, we aimed to evaluate the expression of GRPr and PSMA in a group of patients diagnosed with castration-resistant prostate cancer (mCRPC) by means of PET imaging. Methods: Seventeen mCRPC patients referred for radio-ligand therapy (RLT) were enrolled and underwent [68Ga]Ga-PSMA-11 and [68Ga]Ga-RM2 PET/CT imaging, 8.8 ± 8.6 days apart, to compare the biodistribution of each tracer. Uptake in healthy organs and tumor lesions was assessed by SUV values, and tumor-to-background ratios were analyzed. Results: [68Ga]Ga-PSMA-11 showed significantly higher uptake in tumor lesions in bone, lymph nodes, prostate, and soft tissues and detected 23% more lesions compared to [68Ga]Ga-RM2. In 4/17 patients (23.5%), the biodistribution of both tracers was comparable. Conclusions: Our results show that in our cohort of mCRPC patients, PSMA expression was higher compared to GRPr. Nevertheless, RLT with [177Lu]Lu-RM2 may be an alternative treatment option for selected patients or patients in earlier disease stages, such as biochemical recurrence.
背景：胃泌素释放肽受体（GRPr）在多种实体瘤中高度过表达，包括初治和复发性前列腺癌。[68Ga]Ga-RM2是用于GRPr PET成像的成熟放射性示踪剂，而[177Lu]Lu-RM2已被提议作为前列腺特异性膜抗原（PSMA）表达异质性和/或低表达患者的治疗替代方案。本研究旨在通过PET成像评估一组诊断为去势抵抗性前列腺癌（mCRPC）患者的GRPr与PSMA表达情况。方法：纳入17例拟接受放射性配体治疗（RLT）的mCRPC患者，分别进行[68Ga]Ga-PSMA-11与[68Ga]Ga-RM2 PET/CT成像（间隔8.8±8.6天），比较两种示踪剂的生物分布特征。通过标准化摄取值评估健康器官与肿瘤病灶的摄取情况，并分析肿瘤背景比。结果：[68Ga]Ga-PSMA-11在骨、淋巴结、前列腺及软组织肿瘤病灶中的摄取显著高于[68Ga]Ga-RM2，且多检出23%的病灶。在4/17例（23.5%）患者中，两种示踪剂的生物分布具有可比性。结论：本研究队列数据显示，mCRPC患者的PSMA表达高于GRPr。尽管如此，对于特定患者或疾病早期（如生化复发期）患者，[177Lu]Lu-RM2放射性配体治疗仍可作为潜在替代治疗方案。
肿瘤(癌症)患者之家