Comparing the Urinary Radioactivity of PET Radiotracers: What a Multicenter Study Reveals

Multicenter prospective research shows that the positron emission tomography (PET) radiotracer ¹⁸F‑flotufolastat offers significantly lower urinary radioactivity in comparison to ¹⁸F‑piflufolastat, according to study findings presented at the American Society of Clinical Oncology Genitourinary Cancers (ASCO-GU) Symposium.

For the intra-patient comparator study, researchers compared ¹⁸F‑flotufolastat (Posluma, Blue Earth Diagnostics) and ¹⁸F‑piflufolastat (Pylarify, Lantheus) in 55 men who had prostate-specific antigen (PSA) levels (< 0.5 ng/mL) and biochemical recurrence of prostate cancer (PCa) > six months after undergoing radical prostatectomy.

The study findings revealed that ¹⁸F-flotufolastat offered a significantly lower median bladder SUVmean (10.9 vs. 29) and over an 18 percent higher detection of PCa recurrence (45.5 percent vs. 27.3 percent) in comparison to ¹⁸F‑piflufolastat.

“There was a higher accumulation of radiotracer within the bladder for the ¹⁸F‑piflufolastat compared to ¹⁸F-flotufolastat and that … limited the ability to detect, certainly, recurrence,” maintained study author Brian Helfand, M.D., chief of the Division of Urology and associate chief scientific officer at Endeavor Health in Evanston, Ill. “ … Subsequently, the planning you can envision was very different based on the ability to find and localize lymph nodes and other kind of local recurrence that was not possible with the ¹⁸F‑piflufolastat.”

Dr. Helfand is bullish about the ability of future research to not only discern key differences between PET radiotracers but to further examine their capability to facilitate earlier detection of smaller lesions.

“I would say that the current limit of (lesion) resolution of any of these agents is about four millimeters, but we may be even pushing that further, ideally getting equivalent to the microscopic level so we can really detect disease very early on, and most accurately,” added Dr. Helfand.

(Editor’s note: For related content, see “Can 18F-Flotufolastat Bolster Detection of PCa Recurrence in Patients with Low PSA Levels After Radical Prostatectomy?,” “Comparative PET Imaging Trial Shows Increased Detection of PCa Recurrence with 64Cu-SAR-bisPSMA” and “Study: PSMA PET/CT Changed Treatment Plans for Over a Third of Men with Prostate Cancer.”)