A blue ribbon is a symbol of prostate cancer awareness. Men don't need to worry about rises in their PSA if their overall level is low, doctors say. (iStock)

A rising PSA level isn't such a good predictor of prostate cancer after all and can lead to many unnecessary biopsies, says a large new study.

Most men over 50 get PSA blood tests, but they're hugely problematic. Too much PSA, or prostate-specific antigen, only sometimes signals prostate cancer is brewing — it also can mean a benign enlarged prostate or an infection. And screening often detects small tumors that will prove too slow-growing to be deadly. Yet there's no sure way to tell in advance who needs aggressive therapy.

On the other hand, some men have cancer despite a "normal" PSA count of 4 or below. So for PSAs that are rising, yet still in the normal range, some guidelines urge doctors to consider a biopsy.

How quickly the PSA number rises is something "that patients and doctors worry a lot about," said Dr. Andrew Vickers of Memorial Sloan-Kettering Cancer Center. "Men show up here with a PSA of 2 and we say, 'Why are you here?' And they say, 'Well, I used to be a 1 and my doctor's worried. Am I going to die?'"

So Sloan-Kettering researchers studied whether considering PSA velocity adds value to the biopsy-or-not decision in those otherwise low-risk men — and concluded it doesn't.

"This is a really important study," said Dr. Otis Brawley of the American Cancer Society, who wasn't part of the research. "A lot of doctors are going to stop looking at a PSA rise of 1 and ordering biopsies."

Vickers' team tracked 5,519 men who'd taken part in a huge prostate cancer prevention study and who'd received a biopsy at the study's end regardless of their PSA level.

Just having a rising PSA — if nothing else was considered — was associated with a slightly higher risk of having cancer, although not the more worrisome aggressive kind. But the PSA level alone, not its rise, was a much better predictor of a tumor, reported Vickers, a statistician who specializes in prostate cancer.

Focusing on PSA's rise instead triggered many more biopsies, with close to 1 in 7 men who would get one, concluded the study, published in this week's online issue of Journal of the National Cancer Institute.

That compares with 1 in 20 men who are biopsied for a high PSA level alone, noted Dr. Grace Lu-Yao of the University of Medicine and Dentistry of New Jersey in an accompanying editorial.

"There's an important public health message here, which is for men not to worry about changes in their PSA if their overall PSA level is low," Vickers said.