The test seems likely to improve the diagnosis and treatment of a disease that kills 33,000 American men each year.
After doctors found cancer in Dr. Mark Samberg’s prostate last spring, the 70-year-old retired urologist prepared to have his prostate removed. He knew that the surgery would cure him, assuming the cancer was confined to the organ.
But his doctors had a nagging concern — the cancer cells seen on the biopsy were aggressive and may already have escaped from his prostate. If so, the operation would not cure him. The problem for Dr. Samberg, and for many men with aggressive prostate cancer, was this: If there are cancer cells outside the prostate, how can they be found?
Now the Food and Drug Administration has approved a test that can locate prostate cancer cells wherever they are. Exuberant cancer specialists said the test would alter treatment for patients nationwide.
“It’s the most exciting thing in prostate cancer in my lifetime,” said Dr. Kirsten Greene, chair of the urology department at the University of Virginia School of Medicine.
The test relies on a radioactive tag attached to a molecule that homes in on prostate cancer cells that have spread to other locations in the body and may seed new tumors. Once tagged, the clusters of cells appear as bright spots on PET scans.
At the moment, the F.D.A.’s approval applies only to testing at the University of California, San Francisco, and the University of California, Los Angeles, which conducted clinical trials. But several companies hope to market similar tests soon.
“It’s absolutely fabulous,” said Dr. Oliver Sartor, professor of medicine at Tulane University School of Medicine. When he learned that the test had been approved, he said, he danced in his office “and had a toast of imaginary champagne.”
Now specialists are hoping to use the technique to kill cancer cells, not just find them. The idea is to attach a radioactive drug to the molecule that seeks out prostate cancer cells. The molecule will deliver the drug directly to those cells and, it is hoped, the radiation will destroy the cancer. Experiments already have begun at U.C.S.F. and U.C.L.A.
The road to the new test has been long. Nearly 30 years ago, researchers discovered that prostate cancer cells carry a unique protein on their surfaces called prostate specific membrane antigen, or P.S.M.A. More recently, researchers found small molecules that could home in on P.S.M.A.
Scientists theorized that radioactive tracers attached to those molecules could make prostate cancer cells visible on PET scans. In 2010, researchers at the University of Heidelberg in Germany published the first images of prostate cancer cells located in this way.
Over the past four years, studies involving about 1,000 patients by Dr. Jeremie Calais, a nuclear medicine physician at U.C.L.A., and Dr. Thomas Hope, a nuclear medicine physician at U.C.S.F., showed that the scan accurately detected prostate cancer cells anywhere in the body before treatment and even after treatment, when cancer may recur.
The research led to changes in treatment for most patients, including decisions to recommend targeted radiation, guided by the scans, rather than chemotherapy or androgen-blocking therapy, treatments that impact the entire body.
Dr. Hope described two situations in which the PET scans can transform treatment decisions.
Most men learn they have prostate cancer when a simple blood test finds high levels of prostate specific antigen, or P.S.A. The next step is a biopsy of the prostate and removal of cancer cells for examination to see how aggressive they appear.
Men often have MRI scans to see if the capsule surrounding the prostate has been breached — a sign the cancer has gotten out. And doctors consider how high P.S.A. levels are. The higher they are, the more cancer in the body and the more likely it has spread.
The second scenario occurs after a man has had his prostate removed or destroyed by radiation. If the patient’s P.S.A. levels start to rise months or years later, the cancer that doctors thought they had cured had already seeded itself elsewhere in the man’s body.
In both situations, “we know they have disease, but we don’t know where it is,” Dr. Hope said. The new scan seems able to show doctors where to look. The researchers are now conducting studies to see if these treatment revisions ultimately prolong patients’ lives.
Dr. Samberg, who lives in Sacramento, was one of the participants in the U.C.S.F. trial. Before his scheduled prostatectomy, the scan turned up cancerous cells in his bones and lymph nodes. “That was shocking,” he said.
Without the new test, the doctors would have removed Dr. Samberg’s prostate, and they would have realized he still had cancer when his P.S.A. levels began to rise. In such a case, doctors usually irradiate the area where the prostate used to be — the prostate bed, which is the site of remaining cancers a bit more than half the time.
For Dr. Samberg, that procedure, like the prostatectomy, would not have helped. “Standard therapy for me would fail,” he said. Instead, the discovery that his cancer was in his bones and lymph nodes pointed to targeted radiation therapy, hormonal therapy and, most recently, immunotherapy.
“I am in complete remission,” Dr. Samberg said. “I hope it makes a difference long term.”
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