Pilot Evaluation of Anti-1-amino-2-[18F] fluorocyclopentane-1-carboxylic acid (anti-2-[18F] FACPC) PET-CT in Recurrent Prostate Carcinoma

Purpose: Anti-1-amino-2-[F-18]fluorocyclopentane-1-carboxylic acid (anti-2-[F-18]FACPC) is an unnatural alicyclic amino acid radiotracer with high uptake in the DU-145 prostate cancer cell line in vitro. Our goal was to determine if anti-2-[F-18]FACPC is useful in the detection of prostate carcinoma. Procedures: Five patients with elevated PSA (1.1-20.5 ng/mL) after curative therapy for prostate carcinoma underwent 60 min dynamic positron emission tomography (PET) of the pelvis after IV injection of 193-340 MBq of anti-2-[F-18]FACPC. Uptake was compared against PET scans in the same patients with the leucine analog, anti-1-amino-3-[F-18]fluorocyclobutane-1-carboxylic acid (anti-[F-18]FACBC), at similar time points and validated via pathology, clinical, and imaging follow-up. Results: At 5 min, average (+/- SD) SUVmax of malignant lesions is 4.1(+/- 1.3) for anti-2-[F-18] FACPC and 4.3(+/- 1.1) for anti-[F-18]FACBC. Yet, blood pool activity at 5 min is significantly higher for anti-2-[F-18]FACPC with average (+/- SD) lesion/blood pool SUVmax/SUVmean ratio of 1.4 (+/- 0.5) vs. 3.0 (+/- 0.9) for anti-[F-18]FACBC. At 20 min, average (+/- SD) SUVmax of malignant lesions is 2.6 (+/- 1.0) for anti-2-[F-18]FACPC and 3.4 (+/- 0.8) for anti-[F-18]FACBC. Yet, bladder activity at 20 min is significantly more intense for anti-2-[F-18] FACPC with average (+/- SD) lesion/bladder SUVmax/SUVmean ratio of 0.3 (+/- 0.8) vs. 2.3 (+/- 1.4) for anti-[F-18]FACBC. Conclusions: While prostate bed lesions are visible on early imaging with anti-2-[F-18]FACPC, there is high blood pool activity obscuring nodes. As blood pool fades, nodal uptake decreases and high bladder activity then obscures pelvic structures. Compared with anti-[F-18]FACBC, imaging characteristics for anti-2-[F-18]FACPC are unfavorable for pelvic recurrent prostate carcinoma detection.