When patients experience biochemical recurrence, the prostate-specific antigen (PSA) level rises. However, there is no visual evidence of disease on conventional scans. A new study presented at the Genitourinary Cancers Symposium (GUCS) shows that adding an imaging agent (18F-fluciclovine) to the positron-emission tomography (PET)/CT scans provides more information, and this has a substantial impact on clinical decisions for such patients.
For 52 of 85 men enrolled in the study (61%), clinical management was changed after 18F-fluciclovine PET/CT imaging. For some patients, management was changed to provide a better chance at cure or to avoid possibly futile salvage therapy. 18F-fluciclovine is a synthetic amino acid that is taken up by amino acid transporters that are massively upregulated in many cancers, including prostate cancer.
In the FALCON (Fluciclovine [18F] PET/CT in Biochemical Recurrence of Prostate Cancer) study, the investigators recorded the intended management plan for patients being considered for radical salvage treatment after the patients experienced initial biochemical recurrence; the investigators subsequently recorded newly recommended plans following scanning with 18F-fluciclovine.
The primary objective was assessment of the clinical impact of the scanning agent on patient management. Postscan changes to treatment modality, such as a change from salvage radiotherapy (RT) to systemic therapy, were classed as major; changes within a modality (eg, a modification of RT fields) were classed as other. Of the 52 men for whom changes in management were made, 31 underwent a major change.
For 21 patients, changes in management were classified as other. Notably, the median PSA level among the men was 0.63 ng/mL. That median PSA level worried a clinician in the GUCS audience. The investigators wondered whether waiting for disease spread to show up on a scan, even with highly sensitive 18F-fluciclovine PET/CT imaging, might result in missing the window for cure. In the study, not all the scans were positive.
Among men who had already undergone prostatectomy and whose PSA level was <.5, there was a 25% detection rate upon scanning. That would have triggered salvage RT. Furthermore, the study was multicenter, and hypersensitive PSA tests were used heterogeneously in the study. There is a need for robust criteria for employing 18F-fluciclovine scanning. There is no cutoff PSA value with regard to not performing the scan.
The inclusion criteria for the study was a PSA level >0.1 and a doubling time <15 months or a PSA >1, regardless of doubling time. More research is needed. Currently, follow-up is underway to assess whether patients in the current study experienced clinically related outcomes — PSA dropping/stabilizing or increasing — after 18F-fluciclovine scanning. Long-term studies are needed to determine the impact of this tool on disease outcomes.
18F-fluciclovine is well established as a diagnostic tool for detecting sites of recurrent prostate cancer. However, the cutting-edge center had added 18F-fluciclovine scanning only in the past 6 months. If continue to see compelling trends like these namely, fluciclovine changing patient management upwards of 60% of the time, it may show greater clinical implementation, the investigators concluded.