Researchers at UCLA are touting the use of a new imaging method for locating prostate cancer recurrence, compared to the conventional approach.
The team claims in a new study that in the investigational scanning approach, PSMA PET/CT, may offer a better chance of determining the location of recurring cancer following prostate cancer surgery than the current U.S. standard of fluciclovine positron emission tomography, known also as Axumin PET/CT.
"PSMA is an enzyme that is located on the cell surface of prostate cancer cells. The high number of PSMA molecules results in high amounts of ligands binding to this target," Dr. Johannes Czernin, professor of molecular and medical pharmacology at the David Geffen school of Medicine at UCLA, told HCB News. "There is very little PSMA expression in normal cells of the prostate and in other tissues. This is important for imaging because it results in a low background signal. Thus, the target (prostate cancer) to background ratio is very high. The advantage of this high target to background ratio is that relatively small lesions can be detected."
National Comprehensive Cancer Network guidelines call for using 18F-fluciclovine PET-CT for prostate cancer biochemical recurrence localization following radical prostatectomy, whereas European Association of Urology guidelines recommend prostate-specific membrane antigen (PSMA) PET-CT. Patients who undergo prostate cancer surgery must be routinely screened after for a recurrence of cancer. While recurring prostate cancer following surgery is usually in the area where the prostate was removed (prostate fossa), some cases have found cancer to be outside of it, in areas such as bones or lymph nodes.
By injecting patients with fluciclovine, physicians use PET/CT to track amino acids, which the contrast agent mimics due to their radioactive composition. As cancer cells consume more amino acids than regular cells, the technique helps locate the cancer by showing which cells consume more of the fluciclovine. The prostate-specific membrane antigen (PSMA) method uses the antigens’ protein expression levels to locate recurring cancer by tracking the cell surface proteins due to prostate cancer cells over-expressing a high level of PSMAs compared to normal ones.
Researchers tested both methods on 50 patients who previously underwent radical prostatectomy. Each participant had a biochemical recurrence of prostate cancer with low prostate-specific antigen levels, indicating that their cancer recurred at an early stage.
Each man received a fluciclovine scan as part of their post-surgical recurrence standard-of-care treatment, and underwent a PSMA scan within 15 days before or after the standard. Images were then read by three physician readers who were unaware of each others’ findings.
The PSMA scan was found to be more accurate in detecting the recurring prostate cancer, locating it in 56 percent of scans. Fluciclovine, in contrast, detected it only in 26 percent of images.
"Together with a group from UCSF led by Dr. Thomas Hope, we are conducting large scale phase three clinical trials at UCSF to establish the accuracy of PSMA PET/CT imaging in various clinical situations," said Czernin. "These data have been analyzed and will be submitted to the FDA for a New Drug Application (NDA) within the next few weeks. FDA approval is, of course, a prerequisite to establish PSMA imaging as the new standard of care in biochemical recurrence of prostate cancer."
Production of Axumin is carried out by Blue Earth Diagnostics, which has been seeking to increase access to the agent throughout Europe. The company was recently bought by Bracco Imaging, an agreement which is expected to expand the presence of Blue Earth Diagnostics (and perhaps, Axumin) into more than 100 markets. https://www.dotmed.com/news/story/47223 https://www.dotmed.com/news/story/47756
Axumin is currently approved for use in the U.S. and Europe. PSMA PET/CT is investigational and is not FDA approved.
The findings were published in The Lancet Journal