Evaluation of the 18F-labeled L-glutamate derivative 18F-FSPG (BAY 94-9392) in brain and head and neck cancer patients

274 Objectives (S)-4-(3-[18F]Fluoropropyl)-L-glutamic acid (18F-FSPG alias BAY 94-9392) is a novel radiopharmaceutical developed by Bayer HealthCare for PET imaging (FDA eIND 108509). It is a glutamate analogue that shows promise for oncologic imaging. We present data on 5 brain and 5 head and neck cancer subjects. Methods Approximately 8 mCi (± 10%) of 18F-FSPG was given i.v. to 10 subjects (mean age: 59 ± 16 years) and 7 PET and 3 CT scans were acquired per patient over the next 2 hours. Vitals, EKGs and blood samples were obtained before and after imaging. Seven subjects also had a clinical 18F-FDG PET/CT scan within 1 month. SUV measurements (including unpaired T-tests) and visual comparison of the 18F-FSPG and 18F-FDG scans were done to assess relative efficacy and differences between these tracers. Results 18F-FSPG did not cause alterations in symptoms, vitals, EKGs, or lab values. There was similar distribution in all patients with primary clearance through the kidneys. Quantitatively, all malignant lesions were positive on 18F-FSPG but with a range of uptake (see table). Compared to the 18F-FDG scan, the 18F-FSPG scan showed lower absolute SUV values in the lesions, but higher tumor-to-background levels. This was confirmed visually in that 18F-FSPG showed higher uptake than 18F-FDG for brain lesions and similar uptake for head and neck lesions, but with less background brain uptake. However, these differences were not significantly different. Conclusions 18F-FSPG was well tolerated and showed increased uptake in both brain and head and neck cancer. Markedly lower background uptake than 18F-FDG, especially in the brain, appears to be beneficial. These results are promising and warrant further analysis in a larger cohort of subjects