PSA tests and the risk of overdiagnosis

Many people are diagnosed with a condition or even a cancer that won’t affect them in any significant way. Medical experts call this “overdiagnosis.”

The poster child of overdiagnosis is prostate cancer screening. When the PSA test, which can detect minute quantities of prostate specific antigen in the blood, was introduced nearly 20 years ago, the test became widely used as a routine check for men over age 40. But the test produced a high rate of false positives, and it also exposed benign, microscopic cancers that in many cases led to radiation treatment and surgery.

In a 2009 study, researchers found that use of the PSA test led to 1.3 million American men being diagnosed and more than a million treated — “all for a cancer that was never going to bother them,” says study author Dr. H. Gilbert Welch, a physician and professor at Dartmouth Medical School in Hanover, N.H. He’s also the author of “Overdiagnosed: Making People Sick in the Pursuit of Health.”

About a third of these men suffered substantial side effects from the cancer treatment, including bowel, bladder and sexual dysfunction. And a few men died of the treatments.


A separate 2009 study in the New England Journal of Medicine found that 1,410 men would have to be screened in order to prevent one man from dying of prostate cancer. But to save that one person from prostate cancer, 48 men would have to be treated unnecessarily.

“And that treatment has real side effects,” says Welch. “I look at that deal, and I say that’s a bad deal.”

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