Probability of a Positive F-18 Fluciclovine Scan based on Level of PSA

Objectives: NTRODUCTION Prostate carcinoma is the second most common cancer diagnosis in men with over 160,000 new diagnoses and over 26,000 deaths in 2016. While most men are diagnosed early, treated adequately, and survive, 20-30% develop a rising PSA post-treatment indicating recurrent or metastatic disease. Until now, there have been few methods available to determine the location and extent of recurrence. The introduction of F-18 fluciclovine PET/CT has provided a sensitive and accurate imaging tool to accurately restage these patients so that appropriate care can be provided. When to apply this restaging exam to provide the most accurate results has yet to be determined and is the purpose of this study. METHODS Fifty-nine men previously diagnosed with and treated for prostate carcinoma developed a rising PSA post-treatment and presented for an F-18 fluciclovine PET/CT scan at our institution. Data collection included age at time of the scan, Gleason score, PSA level prior to PET/CT scan, and PET/CT scan results by location (prostate gland/bed, lymph nodes, soft tissues/skeleton). Logistic regression was used to determine the probability of a positive scan based on PSA level. Point-Biserial correlation was used to determine the correlation between PSA level and extent of disease. RESULTS The average age of the men in this group was 69.3 years (range 49-93 years). The Gleason score (GS) at the time of diagnosis was GS6 = 12, GS7 = 22, GS8 = 7, GS9 = 9, GS10 = 2; the Gleason’s score was unknown in 7 patients. The median PSA level prior to the F-18 fluciclovine PET/CT was 2.4 (range 0.21-91.1). The number of positive PET/CT scans was 38 (64.4%) and the number of negative scans was 20 (33.8%); there was 1 equivocal scan. The location of positivity was prostate gland/bed = 26, lymph nodes = 20, soft tissues/skeleton = 12. The probability of a positive scan based on PSA level was: 40% at 0.72, 50% at 1.80, 60% at 2.88, 70% at 4.06, 80% at 5.50, and 90% at 7.67. There was a positive correlation between the level of PSA and recurrence in the prostate gland/bed (0.327, p = 0.0138) and in lymph nodes (0.329, p