Aim

⁶⁸Ga-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 ⁶⁸Ga-RM2 in 95 patients with biochemically recurrent (BCR) PC.

Materials and methods

Ninety-five participants had simultaneous PET/MRI for BCR PC and were prospectively enrolled in this study. Maximum standardized uptake value (SUV_max) and mean standardized uptake value (SUV_mean) 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_mean was less than SUV_mean of the aortic arch (AA); mild if SUV_mean was less or equal to 2.5, but higher than SUV_mean of the AA; moderate if SUV_mean was higher than 2.5, but less or equal to 5; intense if SUV_mean was higher than 5.

Results

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_max measurements (average SUV_max 64.91). Mild and moderate uptake was measured in the esophagus (average SUV_max 3.99), while the stomach wall, duodenum, and rectum had mild uptake (average SUV_max 2.49, 3.42, and 3.58, respectively).

Conclusions

⁶⁸Ga-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.

中文翻译：

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生化复发性前列腺癌患者的生理68Ga-RM2摄取：半定量测量图集。

目的

⁶⁸ Ga-RM2是一种蛙皮素（BBN）类似物，其靶向在包括前列腺癌（PC）在内的许多癌细胞中过表达的胃泌素释放肽受体（GRPR）。据报道，它可以成功检测出主要和复发的PC。在这里，我们描述了95例生化复发（BCR）PC患者中⁶⁸ Ga-RM2的生理吸收分布和范围。

材料和方法

九十五名参与者同时进行了BCR PC的PET / MRI检查，并且前瞻性地参与了这项研究。在每个参与者的24个正常解剖结构中测量最大标准化摄取值（SUV _max）和平均标准化摄取值（SUV_均值）。三位读者分别评估了这些图像。各种正常组织的摄取被分为4个不同的类别：如果SUV_平均值小于主动脉弓（AA）的SUV_平均值，则无明显摄取；如果SUV_平均值小于或等于2.5，但高于AA的SUV_平均值，则为轻度；如果SUV_平均数高于2.5，但小于或等于5，则为“中等” ；如果SUV_意味着激烈 高于5。

结果

由于放射性示踪剂的排泄，在膀胱中观察到最强烈的摄取。在大脑，唾液腺，肺，心肌，骨骼，肌肉和脂肪中均未见明显摄取。肝，脾和肾上腺几乎没有明显的摄取。胃肠道具有强烈的生理吸收，胰腺是SUV_最大测量值最高的器官（平均SUV_最大64.91）。食道测量到轻度和中度摄取（平均SUV_最大值为3.99），而胃壁，十二指肠和直肠的摄取为轻度（平均SUV_最大值为2.49、3.42和3.58）。

结论

⁶⁸ Ga-RM2主要用于PC检测，但可用于过度表达GRPR的其他肿瘤，例如乳腺癌。健康组织中正常生物分布和SUV测量的地图集将帮助医生区分生理摄取与病理摄取，并可能有助于计划使用GRPR靶向放射性药物的未来研究。