Avoiding False Positives on Prostate Cancer PSMA PET Scans

This episode, "Avoiding False Positives on Prostate Cancer PSMA PET Scans," features the panel reviewing where PSMA tracers normally accumulate in the body and how that pattern can be misread as disease.

Dr. Ghesani reviews the normal biodistribution of PSMA tracers, noting uptake in the salivary glands, liver, spleen, and kidneys, along with excretion into the ureters, bladder, and bowel, with the duodenum typically showing more prominent activity. He explains that these patterns matter directly for treatment planning with lutetium-177 PSMA therapy and for anticipating adverse effects. Dr. Yonover recalls that early in his experience, physiologic uptake in the ganglia produced false positives before readers grew more familiar with the pattern. He emphasizes that PSMA PET shows PSMA expression rather than cancer directly, and that some advanced cancers lose PSMA expression and become invisible on these scans. Dr. Mendel agrees, noting that outside readers still occasionally mistake ureteral activity for a lymph node, and urges clinicians managing these patients to review images themselves rather than relying solely on written reports. He describes identifying unexpected high-grade lesions on PSMA PET even in patients previously managed with active surveillance and suggests indications will likely continue expanding. Dr. Yonover argues that PSMA PET should now be considered standard before prostatectomy, even in favorable intermediate-risk disease warranting surgery, to avoid operating on patients with occult distant or nodal disease that would render surgery futile. Dr. Ghesani adds technical detail on ganglion uptake, explaining that its asymmetry and intensity are physiologic rather than diagnostic, and that SUV cutoffs are unreliable for distinguishing ganglia from disease. He recommends attending to characteristic teardrop shape and anatomic location instead. Returning to Dr. Mendel's point about ureteral activity, Dr. Ghesani recalls publishing an early FDG biodistribution atlas addressing similar pitfalls and recommends routinely reformatting studies into sagittal and coronal planes, where the ureter's course becomes clearly visible and far less likely to be mistaken for pathologic lymphadenopathy on axial images alone.

In "Variation in PSMA PET Adoption for Prostate Cancer Care," the panel will discuss how adoption of PSMA PET differs across practice settings and how that imaging changes conversations with patients.