Flare on Serial Prostate-Specific Membrane Antigen–Targeted 18F-DCFPyL PET/CT Examinations in Castration-Resistant Prostate Cancer

A 71-year-old man with castration-resistant prostate cancer demonstrated a flare phenomenon on Tc-MDP and CT after 10 weeks of enzalutamide. Prostate-specific membrane antigen-targeted F-DCFPyL PET/CT demonstrated minimal uptake at sites of baseline bone and lymph node disease with increasing uptake at sites of osseous disease following therapy. Although this is likely related in part to decreased androgen receptor activity and a consequent increase in prostate-specific membrane antigen expression, other mechanisms (neovascularization, cell infiltration from the bone repair process, osteoblastic turnover, or minimal radiotracer impurity) may also be involved in causing the increased F-DCFPyL uptake at sites of osseous flare.