Pilot Comparison of 68Ga-RM2 PET and 68Ga-PSMA PET in Patients with Biochemically Recurrent Prostate Cancer

Objectives: Glu-NH-CO-NH-Lys-(Ahx)-[⁶⁸Ga(HBED-CC)] (⁶⁸Ga-PSMA) is a positron emission tomography (PET) tracer that can detect prostate cancer relapses and metastases by binding to the extracellular domain of PSMA. ⁶⁸Ga-labeled DOTA-4-amino-1-carboxymethyl-piperidine-D-Phe- Gln-Trp-Ala-Val- Gly-His-Sta-Leu-NH2 (⁶⁸Ga-RM2) is a synthetic bombesin receptor antagonist that targets gastrin-releasing peptide receptors (GRPr). We present pilot data on the biodistribution of these PET tracers in a small cohort of patients with biochemically recurrent prostate cancer (BCRPC). Methods: Seven men (mean age ± SD: 74.3±5.9 year-old) with BCRPC had both ⁶⁸Ga-PSMA PET/CT and ⁶⁸Ga-RM2 PET/MRI scans. The maximum standardized uptake value (SUV_max) and mean SUV (SUVmean) measurements were recorded in normal tissues and areas of uptake outside the expected physiologic biodistribution. Results: All patients had rising prostate-specific antigen (PSA) (mean±SD: 13.5±11.5) and non-contributory conventional imaging. ⁶⁸Ga-PSMA had the highest physiologic uptake in the salivary glands and small bowel, with hepatobiliary and renal clearance noted, while ⁶⁸Ga-RM2 had the highest physiologic uptake in the pancreas, with renal clearance noted. Uptake values uptake outside the expected physiologic biodistribution were not statistically different between ⁶⁸Ga-PSMA and ⁶⁸Ga-RM2; however, ⁶⁸Ga-PSMA localized in a lymph node and seminal vesicle in a patient with no abnormal ⁶⁸Ga-RM2 uptake. Abdominal periaortic lymph nodes were more easily visualized by ⁶⁸Ga-RM2 in two patients due to lack of interference by radioactivity accumulation in the small intestine. Conclusion: ⁶⁸Ga-PSMA and ⁶⁸Ga-RM2 have distinct biodistribution in this small cohort of patients with BCRPC. The findings here indicate that additional work is needed to understand the expression of PSMA and GRPr in different types of prostate cancer.

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from #Med Blogs by Alexandros G.Sfakianakis via Alexandros G.Sfakianakis on Inoreader http://ift.tt/1NR2E0D
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