Combined Quantification of 18F-FDG and 68Ga-DOTATATE PET/CT for Prognosis in High-Grade Gastroenteropancreatic Neuroendocrine Neoplasms.

RATIONALE AND OBJECTIVES: High-grade gastroenteropancreatic neuroendocrine neoplasms (G3 GEP-NENs) are pathologically classified into well differentiated neuroendocrine tumors (G3 NETs) and poorly differentiated neuroendocrine carcinomas (G3 NECs). Using a novel parameter, we examined the prognostic value of 18F-FDG and 68Ga-DOTATATE PET/CT quantification in comparison to pathologic assessment in G3 GEP-NENs. MATERIALS AND METHODS: A total of 31 patients with G3 GEP-NENs were reviewed. For each patient, the SUVmax on 18F-FDG and 68Ga-DOTATATE PET/CT were used to calculate the FDG-DOTATATE-Z (FDZ) score: a continuous parameter that increases with 68Ga-DOTATATE uptake and decreases with 18F-FDG uptake. The variation in the FDZ score with respect to pathologic variables was examined. Kaplan-Meier and Cox regression analyses were performed to evaluate the effect of FDZ score on overall survival. An external cohort of 21 patients was used for validation. RESULTS: The FDZ score was significantly higher in G3 NETs compared to G3 NECs (p<0.001), and was inversely correlated with Ki67 index (R2=0.33, p<0.001). Patients in the FDZ>0.05 group showed significantly longer survival compared to those in the FDZ≤0.05 group, with median of 34.9 vs. 12.0 months (p<0.001). On univariate regression, FDZ>0.05 (p=0.005), well differentiated disease (p=0.044), and lower Ki67 index (p=0.042) were predictors of survival. On multivariate regression, only FDZ>0.05 could independently predict longer survival with HR=0.16 (p=0.018), which was reproduced in the external validation cohort. CONCLUSION: Combined quantification of 18F-FDG and 68Ga-DOTATATE PET/CT into a novel parameter, the FDZ score, reflects the pathologic characteristics of G3 GEP-NENs and is a prognostic indicator of overall survival independent of differentiation.

Results of a Prospective Trial to Compare 68Ga-DOTA-TATE with SiPM-Based PET/CT vs. Conventional PET/CT in Patients with Neuroendocrine Tumors.

We prospectively enrolled patients with neuroendocrine tumors (NETs). They underwent a single 68Ga-DOTA-TATE injection followed by dual imaging and were randomly scanned using first either the conventional or the silicon photomultiplier (SiPM) positron emission tomography/computed tomography (PET/CT), followed by imaging using the other system. A total of 94 patients, 44 men and 50 women, between 35 and 91 years old (mean ± SD: 63 ± 11.2), were enrolled. Fifty-two out of ninety-four participants underwent SiPM PET/CT first and a total of 162 lesions were detected using both scanners. Forty-two out of ninety-four participants underwent conventional PET/CT first and a total of 108 lesions were detected using both scanners. Regardless of whether SiPM-based PET/CT was used first or second, maximum standardized uptake value (SUVmax) of lesions measured on SiPM was on average 20% higher when comparing two scanners with all enrolled patients, and the difference was statistically significant. SiPM-based PET/CT detected 19 more lesions in 13 patients compared with conventional PET/CT. No lesions were only identified by conventional PET/CT. In conclusion, we observed higher SUVmax for lesions measured from SiPM PET/CT compared with conventional PET/CT regardless of the order of the scans. SiPM PET/CT allowed for identification of more lesions than conventional PET/CT. While delayed imaging can lead to higher SUVmax in cancer lesions, in the series of lesions identified when SiPM PET/CT was used first, this was not the case; therefore, the data suggest superior performance of the SiPM PET/CT scanner in visualizing and quantifying lesions.

A Feasibility Study Showing [68Ga]Citrate PET Detects Prostate Cancer.

PURPOSE: The management of advanced or recurrent prostate cancer is limited in part by the lack of effective imaging agents. Metabolic changes in prostate cancer have previously been exploited for imaging, culminating in the recent US FDA approval of [11C]choline for the detection of subclinical recurrent disease after definitive local therapy. Despite this milestone, production of [11C]choline requires an on-site cyclotron, limiting the scope of medical centers at which this scan can be offered. In this pilot study, we tested whether prostate cancer could be imaged with positron emission tomography (PET) using [68Ga]citrate, a radiotracer that targets iron metabolism but is produced without a cyclotron. PROCEDURES: Eight patients with castrate-resistant prostate cancer were enrolled in this single-center feasibility study. All patients had evidence of metastatic disease by standard of care imaging [X-ray computed tomography (CT), bone scan, or magnetic resonance imaging (MRI)] prior to PET with [68Ga]citrate. Patients were intravenously injected with increasing doses of [68Ga]citrate (136.9 to a maximum of 259 MBq). Uptake time was steadily increased from 1 h to approximately 3.5 h for the final 4 patients, and all patients were imaged with a PET/MRI. Qualitative and semi-quantitative (maximum standardized uptake value (SUVmax)) assessment of the metastatic lesions was performed and compared to the standard of care imaging. RESULTS: At 1- and 2-h imaging times post injection, there were no detectable lesions with [68Ga]citrate PET. At 3- to 4-h uptake time, there were a total of 71 [68Ga]citrate-positive lesions (67 osseous, 1 liver, and 3 lymph node). Of these, 65 lesions were visible on the standard of care imaging (CT and/or bone scan). One PET-avid osseous vertebral body metastasis was not apparent on either CT or bone scan. Twenty-five lesions were not PET-avid but seen on CT and bone scan (17 bone, 6 lymph node, 1 pleural, and 1 liver). The average of the maximum SUVs for bone or soft tissue metastases for patients treated at higher doses and uptake time was statistically higher than the corresponding parameter in normal liver, muscle, and bone. Visually obvious blood pool activity was observed even 3-4 h post injection, suggesting that further optimization of the [68Ga]citrate imaging protocol is required to maximize signal-to-background ratios. CONCLUSIONS: Our preliminary results support that PET with [68Ga]citrate may be a novel tool for imaging prostate cancer. Future studies are needed to determine the optimal imaging protocol, the clinical significance of [68Ga]citrate uptake, and its role in therapeutic decisions.

Calciphylaxis and bone scintigraphy: case report with histological confirmation and review of the literature.

We present a patient with a history of end-stage renal disease, who developed skin lesions in the bilateral calves a month after the initiation of hemodialysis. The lesions were biopsied, and the histological findings were consistent with a diagnosis of calciphylaxis. The patient had a baseline pretreatment bone scan that showed extensive systemic disease. The patient died 20 days after the imaging study. A review of the literature on bone scans and calciphylaxis is presented.