PSMA is a molecule that sits on the surface of prostate cancer cells, and we can look right at it. It can’t hide from us – even in bits of cancer no bigger than a grain of rice – because, thanks to research funded by PCF, newly-approved radioactive tracers that bind to PSMA can shine the spotlight on it in a PET scan.
“If we can see it, we can target it for treatment,” says medical oncologist and PCF-funded scientist Michael J. Morris, M.D., of Memorial Sloan Kettering Cancer Center. “If the cancer cells light up on the PET scan, that tells us that they are likely to be responsive to PSMA-targeting therapy.” The first PSMA-targeting therapy approved in the U.S. – with more being tested now in clinical trials – is LuPSMA (177Lu-PSMA-617; Pluvicto®).
In the phase 3 VISION trial, LuPSMA– an ultra-focused drug called a radioligand that delivers cancer-killing radiation to cells containing PSMA – was shown to make a significant improvement in quality of life, to delay progression of prostate cancer and extend survival.
How do you know if your cancer cells make enough PSMA for this treatment to be effective for you? The way to find out is to have a PSMA-PET imaging test. In March 2022, the FDA approved this novel “theranostic” (an approach using one radioactive drug to find the cancer, and another radioactive drug to treat it) medicine – requiring a certain kind of PSMA-PET test, one that uses gallium-68 (not PYLARIFY®).
The FDA approval is “very specific,” says Morris, “because in the registration trial, only one kind of PSMA-PET scan was used, the gallium-68 scan. Both of these scans are now FDA-approved, and their performance is really quite similar.” It came as a surprise, then, that the approval “only covered gallium-68 as the PET scan associated with eligibility for Lutetium.”
What if you’ve already had or only have access to a PYLARIFY PET scan? Morris explains, “PYLARIFY scans and gallium-68 PET scans perform very similarly in identifying prostate cancers that express PSMA.” For this reason, national guidelines for treating prostate cancer have clarified that from a medical perspective, PYLARIFY scans and gallium-68 scans should be treated equally for identifying men who are, or could be, candidates for LuPSMA. For that reason, many centers will now accept either form of PSMA PET scan. “The best kind of PSMA PET scan,” says Morris, “is the one that you have access to.”
Read next: LuPSMA: The Specifics (Part 2)