Novel Radiotracer Targeting PSMA Shows Promise for Prostate Cancer Detection

The novel radiotracer ¹⁸F-rhPSMA-7.3, which targets prostate-specific membrane antigen (PSMA), is safe and effective in detecting prostate cancer on positron emission tomography/computed tomography (PET/CT) in men with biochemical recurrence. The FDA recently approved the radiohybrid tracer, marketed as Posluma.

“¹⁸F-rhPSMA-7.3-PET provides another diagnostic option that can be used to correctly restage patients with recurrent prostate cancer,” Ashesh B. Jani, MD, of Winship Cancer Institute, Emory University in Atlanta, Georgia, and colleagues wrote in The Journal of Urology. Other FDA-approved radiotracers targeting PSMA include ⁶⁸Ga-PSMA-11 and ¹⁸F-DCFPyL.

In the SPOTLIGHT trial (NCT04186845), 389 men with PSA elevation suspicious for recurrence following definitive radiation therapy or definitive surgery with or without salvage radiation therapy underwent PET/CT approximately 1 hour after intravenous administration of 296 MBq ¹⁸F-rhPSMA-7.3. The overall detection rate was 83%, the investigators reported. The verified detection rate (the overall detection rate multiplied by positive predictive value) was 51% to 54%, exceeding a prespecified threshold for statistical significance of 36.5%. The combined region-level positive predictive value was 46% to 60% and did not meet the prespecified threshold of 62.5%. In the subset of 69 patients with histopathology as a “standard of truth,” however, both the verified detection rate (81%) and the combined region-level positive predictive value (72%) met statistical criteria.

“More than two-thirds of the population had negative baseline conventional imaging, and the overall [detection rate] and [verified detection rate] among these patients support ¹⁸F-rhPSMA-7.3-PET being superior to conventional imaging for the localization of recurrent [prostate cancer],” the investigators wrote.

No significant safety concerns were raised. Of the cohort, 4.1% commonly reported diarrhea, hypertension, injection site reactions, and headache. According to the investigators, ¹⁸F-rhPSMA-7.3 has lower urinary excretion than the currently approved PSMA tracers, “which may enhance visualization of the prostate region.”

In an accompanying editorial, Michal Eifer, MD, of the Department of Diagnostic Imaging, Chaim Sheba Medical Center in Ramat Gan, Israel, and colleagues commented:

“SPOTLIGHT provides compelling evidence that ¹⁸F-rhPSMA-7.3 is superior to conventional imaging with bone scintigraphy, CT, MRI, or other PET tracers like choline, ¹⁸F-NaF, or ¹⁸F-fluciclovine. However, the study does not provide comparative effectiveness of ¹⁸F-rhPSMA-7.3 to the established FDA-approved PSMA PET imaging tracers ¹⁸F-DCFPyL3 and ⁶⁸Ga-PSMA-11.”

Disclosure: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.

References

Jani AB, Ravizzini GC, Gartrell BA, et al. Diagnostic performance and safety of 18F-rhPSMA-7.3 positron emission tomography in men with suspected prostate cancer recurrence: results from a phase 3, prospective, multicenter study (SPOTLIGHT). J Urol. 2023 Aug;210(2):299-311. doi:10.1097/JU.0000000000003493

Eifer M, Hope TA, Calais J, Hofman MS. Editorial comment. J Urol. 2023 Aug;210(2):310. doi:10.1097/JU.0000000000003493.01

This article originally appeared on Renal and Urology News