Dr. Kuo on flotufolastat F 18 utility in patients with high-risk prostate cancer

Opinion
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"We had very high specificities. The specificities amongst the 3 readers ranged from 92% to 96%," says Phillip H. Kuo, MD, PhD, FACR.

In this video, Phillip H. Kuo, MD, PhD, FACR, highlights findings from a subgroup analysis of the LIGHTHOUSE trial (NC04186819), which was presented at the 2023 American Society for Radiation Oncology (ASTRO) annual meeting in San Diego, California. Kuo is a professor of medical imaging and biomedical engineering and medicine at the University of Arizona College of Medicine in Tucson, Arizona.

Video Transcript:

Could you describe the background of this study?

Thank you for this opportunity to address your audience about the very excitingly newly approved earlier this summer PSMA PET radiopharmaceutical flotufolastat F 18. Flotufolastat F 18 has the trade name Posluma, and for those of you who want to read about it more in the scientific literature, it was originally called 18F-rhPSMA-7.3. Interestingly, the rh stands for radiohybrid. This molecule is designed to have an F 18 label for PET imaging, but it also has a metal chelating arm that can be used to bind therapeutic metals for beta isotope therapy, for example, to attack the tumors in a true theranostic paradigm. However, this radiopharmaceutical in the FDA registrational trials is only used as a diagnostic agent. Those 2 phase 3 registrational trials were called LIGHTHOUSE and SPOTLIGHT. LIGHTHOUSE, which was the subgroup analysis for the poster presented at ASTRO today, involved recruitment of men with treatment naive, unfavorable intermediate to very high-risk prostate cancer. All these men were scheduled to undergo radical prostatectomy and pelvic lymph node dissection, which aid in our ability to get the histopathologic standard of truth for the pelvic disease. SPOTLIGHT was for the men with biochemical recurrence, and that also got FDA approval. So, we have indications in both the treatment naive patient population that is scheduled to undergo surgery, as well as the patient population for biochemical recurrence.

What were the notable findings presented at ASTRO?

So what we endeavored to do on this research that's being presented at ASTRO is that we look specifically at the LIGHTHOUSE patient population subgroup that had high-risk to very high-risk prostate cancer. On top of that, those patients had N0M0 conventional imaging. So, by conventional imaging, they were going to go to surgery with no inclination that they had nodal or distant metastatic disease. So, we had 197 patients that fit into that category. We looked first at 174 of those men who underwent surgery and looked at the sensitivity and specificity. There were 3 blinded central readers in this analysis. The sensitivity ranged amongst the 3 readers from 24% to 33%. That's generally in the range of what we see with the other PSMA PET agents. That might seem low initially, but you have to recall that PSMA PET, while very sensitive, is not sensitive enough to detect microscopic disease. That still is below the limit of resolution of our current PET technology. So, it's not surprising that the sensitivity for nodal disease detection compared to that of histopathology, where they're looking under the microscope would seem relatively low. Nevertheless, we had very high specificities. The specificities amongst the 3 readers ranged from 92% to 96%.

This transcription has been edited for clarity.

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