Negative 18F-Piflufolastat PET/CT, But Positive 18F-Fluciclovine PET/CT, in a Patient With Biochemically Recurrent Prostate Cancer.

An 83-year-old man with prostate cancer post external beam radiotherapy presented with biochemical recurrence (PSA, 29.7 ng/mL). PSMA-targeted 18F-Piflufolastat PET/CT was performed, but no avid lesions were identified. Given the high PSA and high suspicion for recurrence, an 18F-Fluciclovine PET/CT was performed. Fifteen 18F-fluciclovine-avid pelvic, abdominal, retrocrural, and left supraclavicular nodal metastases were then identified. Although the majority of prostate cancer metastases are avid on PSMA-targeted PET, some metastases are not. This case demonstrates the ability of metabolic tracers such as 18F-Fluciclovine PET to localize and quantitate disease extent in a patient whose metastases are not avid on PSMA-targeted PET.