Radiologist’s Take Home Pointers on F-18 Fluciclovine (Axumin) PET/CT Imaging

1228 Introduction: Prostate cancer (PCa) is the most commonly diagnosed non-cutaneous malignancy among men in the United States (US) representing 9.6% of all new US cancer cases in 2017 [1]. Of all cancers, PCa is the second leading cause of death among American men, just behind lung cancer [1]. Ninety percent of newly diagnosed PCa patients who have localized disease undergo radical prostatectomy (RP) [2]. Of the post-prostatectomy patients, 15 to 35% of them develop biochemical recurrence (BCR) in the first year after surgery [2]. Therapeutically, PCa initially responds to hormone-deprivation therapy. With time, the effects of hormone-deprivation decrease and subsequently PCa becomes castrate resistant (CRPC) and potentially metastatic (mCRPC) [3]. There is an increased need for more specific and sensitive diagnostic radiopharmaceuticals in order to enhance the early detection rate of BCR prior to CRPC transformation. F-18-Fluciclovine was approved by FDA on 5/27/2016 as a diagnostic agent for PET imaging in men with biochemical recurrent prostate cancer after initial therapy. This radiopharmaceutical is a synthetic L-leucine analogue that is transported across cell membranes by amino acid transporters such as LAT-1 (sodium-independent “L” large neutral amino acid transport system) and ASCT2 (alanine, serine, cysteine), which tend to be upregulated in malignant cells [4]. The Emory and Bologna studies showed superior detection rates of recurrence among patients in the F-18 Fluciclovine arm compared to the In-111-capromab and C-11 choline groups respectively, with both groups having patients suspected of prostate cancer recurrence based on rising PSA. Median PSA in the Emory study was 2.9 ng/ml (IQR: 1.1; 8.9) and the Bologna study was 1.44 ng/ml (IQR: 0.78; 2.8 ng/ml) [4,5,6]. The comparison of In-111-capromab pendetide to F-18 Fluciclovine by the Emory group showed the following for extraprostatic sites: sensitivity 10% vs 55%, specificity 86.7% vs 96.7% respectively [5]. In comparing C-11-choline to F-18-Fluciclovine, the Bologna group reported a detection rates of 20% and 40% respectively with no statistical differences (p=0.25) [4]. Overall, F-18-Fluciclovine was well tolerated, with injection site pain and erythema, headache and dysguesia as noted adverse events. Additionally, elevated bilirubin, hypotension and hypertension were also observed [6]. An advantage of F-18-Fluciclovine is its longer half-life of 110 minutes making it more practical for clinical use compared to C-11 production with a shorter half-life of 20 minutes. Another advantage of F-18-Fluciclovine is the very slow renal excretion which makes the radiotracer uptake in the kidneys negligible and little to no activity in the urinary tract or bladder. In comparing F-18-Fluciclovine to C-11-choline with its early high uptake in the kidneys allowing for early excretion and possible masking of small lesion due to physiological activity in the urinary tract and bladder [4]. Objectives: 1) Indications for F-18-Fluciclovine: 2) Patient preparation for F-18-Fluciclovine: 3) Image Acquisition protocol: 4) Image Illustration of normal physiologic distribution: 5) Image Interpretation with emphasis on the Diagnostic Pearls 6) Pitfalls, potential sources of false positive and negative cases 7) Sinai Clinical Examples of F-18-Fluciclovine and subsequent clinical management impact. SUMMARY: F-18-Fluciclovine (Axumin®) provides a great clinical tool for urologists, radiation oncologists and oncologists in the overall clinical management of patients. This radiopharmaceutical is now FDA approved and available, has a longer half life and images can be acquired 5 minutes after injection, all of these features make F-18-Fluciclovine an optimal radiopharmaceutical for imaging suspected recurrent prostate cancer patients.