Christopher DiBlasio, MD, board-certified urologist and urologic surgeon, spoke with Physician’s Weekly about PMSA PET, an effective and precise technology for localizing metastatic prostate cancer. PSMA PET scans use targeted imaging to detect areas of suspected metastasis for initial therapy and suspected recurrence based on an elevated serum PSA level.
PW: Could you further describe what PSMA PET is?
Dr. DiBlasio: PMSA PET scan is a special imaging technique that identifies a protein called PSMA found in higher amounts on prostate cancer cells than on normal cells. It differs from traditional PET scans, which rely on how quickly cells metabolize a certain material as a marker of activity. PMSA PET is a novel way of diagnosing and treating patients with prostate cancer who have advanced disease.
PW: What are the two types of scans used in the PSMA PET scan?
Dr. DiBlasio: The PSMA PET scan is a combination of a CT scan, which is imaging quality, combined with a functional test that involves injecting a radioisotope that links up to the
PSMA protein exhibited on prostate cancer cells. Therefore, it’s not just imaging, but imaging combined with a functional test.
PW: Which patients are the best candidates for this procedure?
Dr. DiBlasio: Presently, we’re mostly using PSMA PET scans on patients who have been previously treated for prostate cancer and have had some degree of recurrence. We want to know the location of the recurrence and how extensive it is. Most patients who are receiving PSMA PET are those that have already been treated and suffered recurrence and we’re staging them to determine next treatment steps. Traditionally, for a certain level of concern—meaning intermediate or high-risk patients with prostate cancer at time of diagnosis—we would order a CT scan and a bone scan. We’ve observed that PSMA PET is quickly supplanting those tests since it demonstrates much higher sensitivity and specificity.
PW: What happens during the procedure?
Dr. DiBlasio: The patient receives an injection of contrast dye intravenously, which takes about an hour to process by the body. Once the dye is excreted and marked on the PSMA antigen, the patient will go through the scanner, which is similar to a traditional CT scan. The scan takes about 25 minutes and we’ll usually have results within a couple of hours.
PW: Could you describe the function of the radiotracer?
Dr. DiBlasio: The radiotracer attaches to the PMSA antigen. There are two tracers: One is gallium, which is more widely available; a second radioisotope, Pylarify, is approved for patients with prostate cancer, but it’s a bit more difficult to obtain. After being administered intravenously, it links up with the targeted protein on the prostate cancer cell. You can observe the activity as it lights up as a bright orange glow on that tissue that’s showing signs of uptake.
PW: Would you like to see a more widespread use of this technology?
Dr. DiBlasio: PSMA PET is easily the best diagnostic tool that we’ve had for prostate cancer. As a physician, I am excited about it. As a potential patient, having a strong family history of prostate cancer, I am extremely excited about it. Both of my grandfathers died from prostate cancer so in a selfish way, I am happy that this technology exists.
The next step, and it is already happening, is the development of the “theranostics” (therapeutics plus diagnostics). Now that we can isolate the areas involved, we can link radioisotopes to a therapeutic agent. It’s “search and destroy” mission, where it will travel selectively to prostate cells and render treatment in a particularly difficult population of patients. This is huge. We’re just at the tip of the iceberg for this, but we’re fortunate that it’s happening in the here and now.
In the 18 months I have been using PSMA PET, it’s revolutionized my practice. So, with theranostics available on a global level, the sky’s the limit.
Click here to listen in on the conversation about PSMA PET.
