The Blind Spot of Prostate-Specific Membrane Antigen Positron Emission Tomography Staging? Intraductal Carcinoma of the Prostate Is Overrepresented in Patients With No Uptake Pattern on Prostate-Specific Membrane Antigen Positron Emission Tomography and High-Grade Prostate Cancer

PURPOSE: Prostate-specific membrane antigen (PSMA) positron emission tomography (PET) is increasingly used to diagnose and stage prostate cancer. A PRIMARY score uses anatomical localization and uptake patterns to improve diagnostic accuracy. We evaluated the histopathology of patients with no uptake pattern (PRIMARY score 1) and the prevalence of intraductal carcinoma of the prostate (IDC-P) in this subset compared with those with an uptake pattern (PRIMARY score ≥2). MATERIALS AND METHODS: F]DCFPyL PSMA PET before radical prostatectomy. All PSMA PET scans were centrally reviewed by nuclear medicine physicians, with PRIMARY scores and quantitative imaging parameters recorded. Perioperative characteristics, Prostate Imaging Reporting and Data System (PI-RADS), and histopathology were collected. The distribution of grade group and other histopathological findings, including IDC-P, were examined according to PSMA uptake patterns. RESULTS: = .026). In the PRIMARY score 1 subset, patients with IDC-P had considerably more pathological grade group ≥ 3 disease than those without IDC-P (100% vs 33%). Eighty-one percent of all patients had PI-RADS scores 4 or 5 on prebiopsy MRI. The study's generalizability is limited by the selection of patients with PRIMARY score 1 disease who subsequently proceeded to surgery. CONCLUSIONS: In patients who are being considered for radical prostatectomy due to adverse clinical, PI-RADS, or biopsy features, a PSMA PET demonstrating no intraprostatic uptake pattern should not be considered inherently a marker for small-volume or lesser-grade disease. Some high-grade cancers, particularly those associated with IDC-P, may not be well visualized on PSMA PET.