This study was designed to analyze the safety, biodistribution, and radiation dosimetry of a gastrin-releasing peptide receptor (GRPR) antagonist PET tracer, Ga-RM26; to assess its clinical diagnostic value in prostate cancer patients; and to perform a direct comparison between GRPR antagonist Ga-RM26 and agonistGa-BBN. Five healthy volunteers were enrolled to validate the safety ofGa-RM26 and calculate dosimetry. A total of 28 patients with prostate cancer (17 newly diagnosed and 11 posttherapy) were recruited and provided written informed consent. All the cancer patients underwent PET/CT at 15-30 min after intravenous injection of 1.85 MBq (0.05 mCi) per kilogram of body weight of Ga-RM26. Among them, 22 patients (11 newly diagnosed and 11 posttherapy) underwentGa-BBN PET/CT for comparison within 1 wk. Tc-MDP (methylene diphosphonate) bone scans were obtained within 2 wk for comparison. GRPR immunohistochemical staining of tumor samples was performed. The administration of Ga-M26 was well tolerated by all subjects, with no adverse symptoms being noticed or reported during the procedure and at 2-wk follow-up. The total effective dose equivalent and effective dose were 0.0912 ± 0.0140 and 0.0657 ± 0.0124 mSv/MBq, respectively. In the 17 patients with newly diagnosed prostate cancer,Ga-RM26 PET/CT showed positive prostate-confined findings in 15 tumors with an SUV of 6.49 ± 2.37. In the 11 patients who underwent prostatectomy or brachytherapy with or without androgen deprivation therapy, Ga-RM26 PET/CT detected 8 metastatic lymph nodes in 3 patients with an SUV of 4.28 ± 1.25 and 21 bone lesions in 8 patients with an SUV of 3.90 ± 3.07. Compared with Ga-RM26 PET/CT, GRPR agonistGa-BBN PET/CT detected fewer primary lesions and lymph node metastases as well as demonstrated lower tracer accumulation. There was a significant positive correlation between SUV derived from Ga-RM26 PET and the expression level of GRPR ( < 0.001). This study indicates the safety and significant efficiency of GRPR antagonistGa-RM26. Ga-RM26 PET/CT would have remarkable value in detecting both primary prostate cancer and metastasis.Ga-RM26 is also expected to be better than GRPR agonist as an imaging marker to evaluate GRPR expression in prostate cancer.

Background:Pulmonary carcinoids (PC) are histologically classified into typical carcinoid (TC) and atypical carcinoid (AC). The diagnosis of pulmonary carcinoid and possibly the differentiation between TC and AC could make a significant effect on the treatment planning as well as prognosis.[1] Several studies have explored the utility of 68Ga-DOTA-Peptide (68Ga-labelled [1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid]-peptide) and 18F-flurodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) in the evaluation of primary pulmonary carcinoids. Therefore, we performed a meta-analysis to evaluate the diagnostic accuracy and prediction efficiency of histological subtypes of these two imaging modalities in primary PC.Methods:Relevant studies were identified by searching PubMed, Web of Science, and EMBASE published from 2006 to 2016. Two authors extracted characteristics of patients and their lesions using predefined criteria.Results:Fourteen studies comprising 352 patients were included in this meta-analysis. The pooled sensitivity of 68Ga-DOTA-Peptide and 18F-FDG PET/CT in detecting pulmonary carcinoid were 90.0% (95% CI = 82.0–95.0%; P = .07; I2 = 49.6%) and 71.0% (95% CI = 66.0–76.0%; P < .001; I2 = 59.3%), respectively. An SUVmax ratio between 68Ga-DOTA-Peptide and 18F-FDG higher than the cutoff value of 4.28 was predictive of TC with 89.3% sensitivity and 100% specificity (AUC, 96.4%; 95% CI, 91.1–100%). The ratio of tumor uptake to atelectatic lung uptake was significantly higher for 68Ga-DOTA-peptide (2.5–91, mean 30.5 ± 28.1) than for 18F-FDG (0.3–10.3, mean 2.1 ± 2.3) (P < .001).Conclusions:Both 68Ga-DOTA-peptide and 18F-FDG are highly sensitive in detecting pulmonary carcinoid, while 68Ga-DOTA-peptide is more sensitive than 18F-FDG (90.0% vs 71.0%). The SUVmax ratio was an accurate predictor of the histopathologic variety of the carcinoid tumor, and 68Ga-DOTA-peptide was better than 18F-FDG in cases with atelectasis.

Objectives The objective of this study was to assess and compare the performance of 68Ga-DOTA-conjugated-somatostatin-receptor-targeting-peptides (68Ga-DOTA-SST) PET/CT, octreoscan-SPECT/CT and 18F-FDG-PET/CT in the detection of tumor-induced osteomalacia (TIO). Methods Relevant studies reporting the performance 68Ga-DOTA-SST PET/CT, octreoscan-SPECT/CT and 18F-FDG-PET/CT in TIO were identified by searching PubMed, EMBASE, and Web of Science (last updated June 2019). Two authors independently extracted the numbers of true and false positives, and true and false negatives. The pooled estimates on a per-patient basis were calculated with 95% confidence interval (CI) obtained using a random-effects model. Results Fourteen studies comprising 346 patients were included in this meta-analysis. The meta-analysis provided the following results on a per-patient analysis. The pooled sensitivities of both 68Ga-DOTA-SST PET/CT (90%, 95% CI 82–95%) and octreoscan-SPECT/CT (83%, 95% CI 75–89%) were found to be significantly higher (P < 0.005) than that of 18F-FDG PET/CT (67%, 95% CI 53–80%). There was no statistically significant difference between the sensitivity of 68Ga-DOTA-SST PET/CT and octreoscan-SPECT/CT (P = 0.161). Owing to the low number of articles with true negative findings, the pooled specificities were not calculated. A total of 287 tumors were identified in 287 patients according to the data the included studies offered. The majority of the tumors were located in the lower extremities (59.6%, 171/287), followed by craniofacial regions (24.0%, 69/287), torso (9.4%%, 27/287), and upper extremities (6.9%, 20/287). Conclusion This meta-analysis demonstrates that somatostatin receptor-based imaging modalities outperformed 18F-FDG PET/CT in the detection of TIO, with 68Ga-DOTA-SST PET/CT performing slightly better than octreoscan-SPECT/CT.