PD54-01 PREDICTORS OF POSITIVE LESIONS IN 18F-FLUCICLOVINE (AXUMIN) PET/CT

Helen Hougen; Nadine Mallak; Sudhir Isharwal; Ryan Kopp; Jen-Jane Liu; Arthur Hung

doi:10.1097/JU.0000000000000956.01

INTRODUCTION AND OBJECTIVE: The 18F-Fluciclovine (FACBC, Axumin) PET/CT scan has higher sensitivity than traditional imaging modalities for the detection of prostate cancer (PCa) recurrence. We aim to identify the PSA characteristics as predictors of a positive FACBC scan. METHODS: 76 patients who underwent the FACBC scan at our institution were identified. Patient demographics, baseline PSA (BPSA), and clinical information were recorded. Scans were deemed positive if definitive lesions were noted at the prostate bed, pelvic lymph nodes (PLN), or skeletal level. Detection rate was the ratio of positive over total scans. PSA velocity (PSAV) was calculated for patients who did not initiate androgen-deprivation therapy 12 months prior to the scan. The BPSA and PSAV were modeled as predictors of having a positive scan using logistic regression. For patients with biochemical recurrence (BCR) after only prior prostatectomy (RP), we assessed predictors of a positive scan. RESULTS: The median BPSA was 2.65 (IQR 0.72 – 4.76). Detection rate increased with increasing BPSA (Figure). Positive scans had higher median BPSA (2.95, IQR 1.85-7.22 vs. 1.20, IQR 0.40-3.74; p = 0.0015) and higher PSAV (2.30, IQR 1.02-5.41 vs. 1.00, IQR 0.47-2.22; p = 0.025) compared with negative scans. A positive read at the skeletal level was associated with higher PSAV (4.29, IQR 2.96-8.64 vs. 1.41, IQR 0.55-2.81; p=0.02); a positive read at the PLN level was associated with higher BPSA (3.95, IQR 1.88-10.80 vs. 1.96, IQR 0.68-3.98; p=0.019). BPSA (AUC = 0.712) was a better predictor than PSAV (AUC = 0.66) of detection rate. Combining the two variables did not improve their predictive ability (AUC = 0.72). In patients who had BCR after only RP (N=36), FACBC had a 53% detection rate, and those who had a positive scan had a higher BPSA (2.72, IQR 1.33-3.55) compared with those with a negative scan (0.61, IQR 0.30-1.91). In this post-RP group, there was no association with PSAV, Gleason score, T stage, or margin status with detection rate. CONCLUSIONS: FACBC PET’s detection rate increases with increasing BPSA. While higher PSAV was associated with higher detection rate, it did not increase the predictive ability of BPSA for a positive scan in prostate cancer patients. For patients with BCR after RP, only higher BPSA was associated with having a positive scan. Our study shows a lower rate of detection than existing literature.

PD54-01 PREDICTORS OF POSITIVE LESIONS IN 18F-FLUCICLOVINE (AXUMIN) PET/CT

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