Part of the new Winship magazine feature on prostate cancer focuses on a PET imaging probe called FACBC, which was developed by radiologists at Emory. 18F-FACBC (anti-1-amino-3-[18F]fluorocyclobutane-1-carboxylic acid, also called “fluciclovine”) has a lengthening track record in detecting recurrent prostate cancer.
Structure of FACBC, from patent application.
Usually in PET imaging, radioactive glucose is injected into the body, and since cancer cells have a sweet tooth, they take up a lot of the radioactive tracer. But plenty of the tracer also appears in the urine, complicating prostate cancer detection efforts, since the prostate is so close to the bladder. In contrast, FACBC is readily taken up by prostate cancer cells, but doesn’t appear as much in urine.
Because of space considerations, we did not include David Schuster’s description of how FACBC’s utility in prostate was first discovered. Several years ago, he and Mark Goodman had begun investigating the probe’s potential in imaging brain tumors and kidney tumors, and used it with a patient with a large renal mass and many enlarged lymph nodes, as described in the radiology newsletter Aunt Minnie.
“Putting two and two together, one would think this is a renal cell cancer with lymph node metastasis,” Schuster said. “When we did the FACBC study, the renal mass did not have much more uptake than normal renal tissue, but the lymph nodes had very intense uptake. This was a very strange thing to us. Why would the lymph nodes have higher uptake necessarily than this large mass that was renal cancer?”
Surgery revealed that the renal tumor was benign but the nodes had prostate cancer. They knew the patient [already] had prostate cancer, but the consensus was that the disease was quiescent…
“This led us to see if this radiotracer would be good for looking at prostate cancer, specifically because of its low native urinary excretion,” he said. “If you look at the history of medical science, it is taking advantage of the unexpected.”
FACBC has its limitations. Because it’s taken up in benign prostate hyperplasia or inflammation, it probably won’t be so useful for evaluating primary prostate cancers. However, studies are underway testing FACBC’s benefits in designing radiation treatments and also in guiding biopsies for patients with recurrent prostate cancer. The technology, licensed from Emory, is being developed commercially by Blue Earth Diagnostics.
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