Detectability Rates and Impact on Management From High-Sensitivity Total-Body 18F-Fluciclovine PET/CT Scans in Patients With Prostate Cancer Biochemical Recurrence

Abstract

<h3>Purpose/Objective(s)</h3> ¹⁸F-fluciclovine, an FDA-approved synthetic amino acid radiopharmaceutical for assessment of prostate cancer (PCa) recurrence, may show modest lesion detectability rates on conventional PET/CT scanners, especially for low PSA levels (< 30%). A total-body PET/CT scanner can provide high-sensitivity imaging and may provide unique opportunity for detecting lower disease burden. In this pilot work, we explored the lesion detectability rates from ¹⁸F-fluciclovine total-body PET/CT in patients with biochemically recurrent PCa and impact on therapeutic decisions. <h3>Materials/Methods</h3> A single-institution, prospective IRB-approved study was conducted. From December 2019 to February 2021, 21 patients (age, 69.7 ± 7.5 yrs) with history of PCa, treated with radical prostatectomy (n = 18), external beam radiation therapy (n = 2) or brachytherapy (n = 1), subsequently presented with biochemical recurrence by American Urological Association criteria. All patients had standard of care¹⁸F-fluciclovine total-body PET/CT scans after a negative or equivocal cross-sectional conventional imaging. PET/CT images were interpreted on patient- and site-basis for any suspicious recurrent/metastatic lesions (prostate bed, N1, M1). Detection rate was measured as percentage per PSA category. A decision regarding treatment was recorded before and after ¹⁸F-fluciclovine PET/CT results and changes were noted. <h3>Results</h3> Fifteen (71%) patients showed detectable lesions in 24 sites: the prostate bed/seminal vesicles (n = 8), N1 station (n = 7), and M1 (n = 9). The latter included M1a (n = 3), M1b (n = 1) and M1c (n = 5) in different combinations. On a patient basis, detection rates were 2/4 (50%), 4/5 (80%), 2/4 (50%), 2/3 (67%) and 5/5 (100%) for the respective PSA categories of < 0.2, 0.2-0.5, 0.51-1.00, 1.01-2.00 and > 2.00 ng/mL. Overall, detection rate was 10/16 (63%) for PSA < 2 ng/mL (compared to published rates of 26% for fluciclovine and 56%for PSMA). Treatment decisions were changed in 18/21 (87%) of patients in the form of conversion to focal ablative radiation therapy (n = 13, 62%), systemic therapy (n = 2, 10%), or active surveillance (n = 1, 5%) or change in the currently received systemic therapy (n = 2, 10%). <h3>Conclusion</h3> Preliminary results demonstrated a promising role for high-sensitivity total-body PET/CT imaging using ¹⁸F-fluciclovine in patients with biochemically recurrent prostate cancer. In this small cohort, detection rates compared favorably to the published historical controls using fluciclovine or even PSMA on conventional PET/CT scanners. The current findings resulted in impactful changes of management in the majority of patients. A larger study is ongoing to validate the current findings.