Science

PSA tests aren't great for diagnosing prostate cancer. Here are some better options in the works

The PSA test is an imperfect way to screen men for prostate cancer. But until recently, it was seen as the best option available.

The test measures the amount of prostate specific antigen, or PSA, in the blood. This protein is produced in the prostate and tends to spike in men with cancer.

The trouble is, there are other things besides prostate cancer that can boost PSA, says Dr. Stacy Loeb, a urologist at NYU Langone Medical Center in New York City. Experts have come to realize that the test caused many men with elevated PSA levels to endure cancer scares — and painful biopsies — for no good reason.

Now, doctors have new tools to help them detect and manage the often-perplexing disease.

“We haven’t had the perfect tests to guide our decisions,” Loeb says. “But we’re making progress. If you’re coming into this now, you’re in a way better situation than you would have been five or 10 years ago.”

The new generation of screening tests — including the Prostate Health Index (or PHI) and the 4Kscore — can help some men avoid unnecessary biopsies. Both tests use total PSA as just one of many inputs to give a clearer picture of prostate health.

The PHI test, which considers total PSA levels along with two specific types of PSA proteins, is more sensitive than the PSA test alone, says Dr. David Penson, chair of urologic surgery at the Vanderbilt-Ingram Cancer Center in Nashville, Tenn. It is most useful for men with PSA levels between 4 and 10 nanograms per milliliter of blood, a gray area where treatment decisions are tricky.

“If I had a PSA of 6, I would definitely want the PHI test,” he says. “If the test suggests I didn’t have cancer, I would feel great about the world.”

The PHI test, approved by the U.S. Food and Drug Administration in 2012, uses a different scale than the PSA test. If your PHI score is below 27, there’s only about a 10% chance that you have cancer, according to the Mayo Clinic. If your score is above 55, there’s about a 50% chance you have cancer.

A 2015 Journal of Urology study of nearly 1,000 men who underwent biopsies for prostate cancer found that about 40% of unnecessary biopsies could have been avoided by simply skipping the procedure in men with a PHI score below 24. Penson notes that some men would want a biopsy even if they had a low PHI score just to be extra sure they didn’t have cancer. But he suspects most men would get enough peace of mind from the score alone.

“A prostate biopsy is not a lot of fun,” he says. “This helps men make an informed decision.”

The 4Kscore is a screening tool that combines a blood test with other information, including a patient’s age, the results from a digital rectal exam, and whether he’s had a previous biopsy that came up negative. Although it is available to doctors, it is not yet FDA-approved to guide treatment decisions.

In studies, the test has effectively predicted which men with slightly elevated PSAs were most likely to develop metastatic cancer. For example, a 2015 study of blood samples collected from more than 12,500 Swedish men found that less than 0.5% of those with PSAs over 4 and a low 4Kscore went on to develop metastatic prostate cancer in the next 20 years, according to the report in European Urology.

Once a biopsy detects cancer, the new tests can also help determine the next step. Doctors can use the PHI score or the 4Kscore to identify the cancers that are most likely to grow and spread, Loeb says. Those cancers require aggressive treatment, but other, less-aggressive ones are better left alone.

This watch-and-wait approach is becoming more popular as doctors try to move away from unnecessary surgeries, she says. Urologists can monitor changes in test results to decide whether it’s time to take action.

The new tests still fall well short of perfection, but they’re definitely an improvement over the simple PSA test, Penson says. Now doctors hoping to spare as many men as possible from needless biopsies without overlooking serious cancers will need to fine-tune their approach.

“Doctors still don’t know how to put the tests to best possible use,” he says.

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