Study on prostate test spreads confusion

PSA: Men with "normal" readings are found to have cancerous cells, and doctors aren't sure what to do next.

Medicine & Science

May 31, 2004|By Erika Niedowski and David Kohn | Erika Niedowski and David Kohn,SUN STAFF

Five years ago, Tony Caputi had a common blood test for prostate cancer known as a PSA. Afterward, he felt relieved: His reading was 1.1, and most doctors believed that anything under 4 was normal.

But during a subsequent internal exam, a physician noticed something suspicious and recommended a biopsy. It turned out that Caputi, then 43, had prostate cancer after all.

"Just based on the PSA alone, I was below the threshold," said Caputi, who works for the American Foundation for Urologic Disease in Linthicum and whose cancer is now in remission.

Caputi's experience reflects the continuing debate over the PSA test, used widely to help identify cancer in the 230,000 men who are diagnosed with it each year.

A study in last week's New England Journal of Medicine found that 15 percent of men with so-called "normal" PSA levels like Caputi's turned out, after a biopsy, to have prostate cancer.

But while some doctors reconsider the PSA's "safe" level, others are still struggling with a more basic question: Does screening for prostate cancer even save lives?

"This is a complicated one because a lot of people are invested in it and a lot of people are doing it already," said Dr. Russell Harris, director of the prevention program at the University of North Carolina School of Medicine. "But when you really look carefully at the evidence, we found that it really wasn't clear whether there was a benefit or not for the cancers that you would find by screening."

In 2002, the U.S. Preventive Services Task Force, an independent panel that decides whether to recommend screening for diseases, didn't find enough scientific evidence to conclude whether PSA testing was harmful or helpful.

The twist with prostate cancer is that most tumors grow slowly. Many don't spread and aren't fatal. But prostate biopsies and, later, surgery to treat them can create multiple risks.

Russell, who led the yearlong review that the task force relied on, said the new study left a key question unanswered: "If we were to find all those [cancers] and then to treat them, would men be better off?"

Two large-scale, prospective studies under way in the United States and Europe are seeking to answer that question, but the findings are still years off. Meanwhile, doctors will be left grappling with where to draw the line between a normal PSA and one that raises a red flag - usually triggering a biopsy.

Some researchers advocate lowering the threshold for PSA, or prostate specific antigen, from 4 nanograms per millileter to 2.5. A strong proponent of that change is Dr. William Catalona, a urology professor at Northwestern University and one of the first doctors to advocate PSA use in the late 1980s. He said lowering the bar will have a "profound impact" because so many more tumors will be found.

But he and others note that so-called "PSA velocity" - the speed at which the levels rise - is often more important than the absolute readings. An annual rise of more than 0.75, he said, should cause concern, while an increase of 2 or more suggests an especially high risk.

Dr. Joseph Adams, a primary care physician in private practice at Greater Baltimore Medical Center, favors a similar approach. "I've diagnosed several cases of prostate cancer in middle-aged men who had a normal or even low PSA, but we could tell that it was trending up slowly," he said. Instead of changing the PSA threshold, Adams suggests refining it, depending on a man's age.

One of the study's authors, Dr. Howard L. Parnes, the director of prostate cancer research in the National Cancer Institute's prevention division, said the findings can be interpreted as a "glass half full" or a "glass half empty."

Most of the cancers detected in men with a "normal" PSA weren't clinically significant, he noted. Only two out of 100 were aggressive, using the broadest definition. And it was unclear whether those would spread or prove fatal.

"It forces us to have the thoughtful discussion of risks and benefits, rather than relying on an arbitrary cut-point below which we say, `You're okay,' and above which we say, `Get a biopsy,' " Parnes explained.

Dr. H. Ballentine Carter, a professor of urology and oncology at the Johns Hopkins School of Medicine, concedes that the current threshold was set rather arbitrarily. But, he said, "The point I'm trying to make is: We don't need to detect more cancers. We need to be smarter about the ones we detect, and that's going to require more discovery."

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