Baratto Lucia, Duan Heying, Laudicella Riccardo, Toriihara Akira, Hatami Negin, Ferri Valentina, Iagaru Andrei
Division of Nuclear Medicine and Molecular Imaging, Department of Radiology, Stanford University Medical Center, Stanford, CA, 94305, USA.
Department of Biomedical and Dental Sciences and Morpho-Functional Imaging, Nuclear Medicine Unit, University of Messina, Messina, Italy.
Eur J Nucl Med Mol Imaging. 2020 Jan;47(1):115-122. doi: 10.1007/s00259-019-04503-4. Epub 2019 Sep 2.
Ga-RM2 is a bombesin (BBN) analog that targets the gastrin releasing peptide receptors (GRPR) overexpressed in many cancer cells, including prostate cancer (PC). It has been reported to successfully detect primary and recurrent PC. Here, we describe the distribution and range of physiological uptake of Ga-RM2 in 95 patients with biochemically recurrent (BCR) PC.
Ninety-five participants had simultaneous PET/MRI for BCR PC and were prospectively enrolled in this study. Maximum standardized uptake value (SUV) and mean standardized uptake value (SUV) were measured in 24 normal anatomical structures for each participant. Three readers evaluated the images independently. Uptake in various normal tissues was classified into 4 different categories: no significant uptake if SUV was less than SUV of the aortic arch (AA); mild if SUV was less or equal to 2.5, but higher than SUV of the AA; moderate if SUV was higher than 2.5, but less or equal to 5; intense if SUV was higher than 5.
The most intense uptake was observed in the urinary bladder, due to excretion of the radiotracer. No significant uptake was seen in the brain, salivary glands, lungs, myocardium, skeleton, muscles, and fat. Liver, spleen, and adrenal glands had mostly no significant uptake; the gastrointestinal tract had intense physiological uptake, with pancreas being the organ with the highest SUV measurements (average SUV 64.91). Mild and moderate uptake was measured in the esophagus (average SUV 3.99), while the stomach wall, duodenum, and rectum had mild uptake (average SUV 2.49, 3.42, and 3.58, respectively).
Ga-RM2 has been mostly evaluated for PC detection, but it can be used for other tumors overexpressing GRPR such as breast cancer. This atlas of normal biodistribution and SUV measurements in healthy tissues will help physicians distinguish between physiological vs. pathological uptake, as well as potentially assist with planning future studies using GRPR targeting radiopharmaceuticals.
Ga-RM2是一种蛙皮素（BBN）类似物，可靶向在包括前列腺癌（PC）在内的许多癌细胞中过度表达的胃泌素释放肽受体（GRPR）。据报道，它能成功检测原发性和复发性前列腺癌。在此，我们描述了95例生化复发（BCR）前列腺癌患者中Ga-RM2的生理摄取分布和范围。
95名参与者因BCR前列腺癌同时接受PET/MRI检查，并前瞻性纳入本研究。为每位参与者在24个正常解剖结构中测量最大标准化摄取值（SUV）和平均标准化摄取值（SUV）。三名阅片者独立评估图像。将各种正常组织的摄取分为4种不同类别：如果SUV小于主动脉弓（AA）的SUV，则无明显摄取；如果SUV小于或等于２.５，但高于AA的SUV，则为轻度摄取；如果SUV高于２.５，但小于或等于５，则为中度摄取；如果SUV高于５，则为强烈摄取。
由于放射性示踪剂的排泄，在膀胱中观察到最强烈的摄取。在脑、唾液腺、肺、心肌、骨骼、肌肉和脂肪中未见明显摄取。肝脏、脾脏和肾上腺大多无明显摄取；胃肠道有强烈的生理摄取，胰腺是SUV测量值最高的器官（平均SUV 64.91）。在食管中测量到轻度和中度摄取（平均SUV 3.99），而胃壁、十二指肠和直肠有轻度摄取（平均SUV分别为2.49、3.42和3.58）。
Ga-RM2主要用于前列腺癌检测评估，但它也可用于其他过度表达GRPR的肿瘤，如乳腺癌。这本关于健康组织中正常生物分布和SUV测量的图谱将帮助医生区分生理摄取与病理摄取，并可能有助于规划未来使用靶向GRPR的放射性药物的研究。
