Studies Cast New Doubt on Prostate Cancer Screening

ANDREW VICKERS: OK, so PSA stands for prostate specific antigen. Antigen is a protein, and it's specific to the prostate, because you only find that protein in the prostate.

So what a doctor does is take a blood sample. And if he or she finds some PSA, some prostate specific antigen in your blood, that's a sign that there's something wrong with your prostate. The prostate should not be leaking chemicals such as the prostate specific antigen into your bloodstream.

The point about the prostate specific antigen is it's specific to the prostate; it's not specific to prostate cancer. All it tells you is you have some kind of problem in your prostate, and that might be due to cancer, but it might also be due to other causes, such as an infection or to benign changes within the prostate.

Generally speaking, men with a higher PSA value -- and we're talking typical values might be, say, four, five, or six -- are at increased risk of cancer.

But even if your doctor tells you, you have -- your PSA test has come back positive, you're still at lower than 50-50 chance of actually having prostate cancer. Most men with an elevated PSA actually do not have prostate cancer.

ANDREW VICKERS: You did see that in the European study. You saw about a 20 percent reduction in death from prostate cancer.

What the European research has pointed out, though, was that a very large number of men had to be treated in order to prevent one death from prostate cancer. It was about, roughly speaking, a 50-1 ratio.

And that's clearly a problem with screening, is you are detecting a lot of prostate cancers that would never impact a man during his life. And, in fact, we've done studies at our own institution examining the prostates of men who've already died of other causes.

And in a 70-year-old man, for example, there's about a 40 percent chance of having detectable prostate cancer on autopsy. And this is obviously, because the man died of other causes, a prostate cancer that would never have affected him and did not affect him during his lifetime.

RAY SUAREZ: So, briefly, is there a simple answer to the question, does prostate cancer screening save lives?

ANDREW VICKERS: I wish there was a simple answer to that question. I think one thing to bear in mind is we do these very large studies. And when it ends, we think, "Right, that's it, the study's ended, we have our answer." And science, really, is a little bit more complicated than that.

I think we need some time to digest the data, try and understand what it means. These studies will continue. We'll continue to follow these men. We'll continue to analyze data from these studies. And then we'll try and understand what that means and make appropriate guidelines for the U.S. public.

What I will say is that what -- the studies were designed way back in the early '90s. And they really did reflect state-of-the-art in the early '90s.

But since that time, we've learned a lot about prostate cancer. And the couple things that we've learned are really very pertinent to the issue of prostate cancer screening.

The problem with prostate cancer screening is that we're detecting too many cancers that won't affect somebody's life, and maybe we're not treating those cancers as well as we might.

What we've learned about prostate cancer in the meantime is how to treat it better and also how to tell who has an aggressive prostate cancer that really needs to be treated and who has a less aggressive prostate cancer that might be treated by what's called active surveillance.

So we're not actually going in and removing the prostate or treating it with radiation. We're just following a man over time, just to make sure that that cancer doesn't become aggressive. So I think our increased knowledge of prostate cancer...

RAY SUAREZ: I'm going to have to stop it there, Andrew Vickers, but thanks a lot for helping us out in New York.

ANDREW VICKERS: Thank you very much.