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Six questions about prostate cancer screening

Prostate cancer is the second leading cause of cancer death among men, and it's something of an enigma. Unlike cancer in most other sites, tumors aren't surgically extracted from the prostate. Instead, the entire prostate is removed, leading to short- and long-term side effects in patients. Also, it may be the only type of cancer that is diagnosed via blind biopsy - the urologist never actually sees the tumor and must resort to taking multiple needle-stick samples from throughout the prostate. Even when the presence of cancer is confirmed, there's still a great amount of inaccuracy in determining its stage (or relative aggressiveness).

Judging prostate cancer's aggressiveness is very important because despite the number of men it kills, the vast majority of cases are not life threatening. Most affected men have very slow-growing tumors that they will die with rather than from. And because the side effects of treatment - including urinary and sexual dysfunction - can greatly affect men's quality of life, the medical challenge is to correctly assess which men require treatment and which do not.

James Brooks, MD, is a professor of urology and a member of the Stanford Cancer Institute. He has been caring for prostate cancer patients and conducting laboratory and clinical research at Stanford for more than 16 years, and he recently answered some basic questions about prostate cancer screening for me.

What is the PSA test?

PSA stands for "prostate specific antigen," referring to a protein made exclusively in the prostate. We measure the relative level of PSA as an indication that cancer might be present. To be clear, though, the PSA test is not a cancer test. Lots of different things can make PSA level go up, including infections, enlarging of the prostate - which happens as we age - and other things that have nothing to do with cancer.

Who should get a PSA test, and how often?

Recently released guidelines from the American Urological Association advise that for men at an average risk for prostate cancer, they should get a PSA test every other year beginning at age 55 and stop at age 69. If a man has a family history of prostate cancer, or is of African American descent, it is probably better to begin at age 40 or 45, and if their first score is very low he can wait up to five years to get another test.

What has been the impact of the PSA test?

I think it is pretty clear that screening has made a difference in survival rates. Prostate cancer death rates were slowly rising for many years. Then in the late 1980s we started screening with the PSA test. Deaths from prostate cancer peaked in 1994, and they are now 40 percent lower than they were at that peak. Two things changed since 1994: aggressive screening and aggressive treatment of prostate cancer.

All of this screening has in a sense changed prostate cancer. It used to be that men presented with more advanced prostate cancer. For example, in 1990, one in five men who walked into my office had prostate cancer that had already spread outside the prostate. Now only one in 25 men has metastatic disease.

So what is the debate over screening?

The question is how often does screening and treatment save lives versus how often are we finding cancers that are not life threatening, yet men are still getting treatments with the potential of serious physical, emotional and financial side effects?

When we started screening with PSA we found the big, bad cancers. As we have screened more men more often we now find smaller, earlier stage cancers. Finding cancer and treating it earlier would seem to be a good thing, but the problem is that we are increasingly finding small, indolent cancers. Men are given a diagnosis of prostate cancer, but we can't be sure whether theirs is life threatening or not. Given that situation, most men opt for treatment.

It would be a non-issue if the treatments had no side effects, but the treatments we currently have - surgery and radiation therapy - can have real, life-changing consequences.

What about the new "genomic" test to assess a tumor's aggressiveness?  

Cancer is a genetic disease and we are beginning to identify some of the specific genes associated with more aggressive cancers. A company called Genomic Health has analyzed gene expression data in cancers from many studies and come up with a short list of genes that are involved in aggressive cancers. In fact, the roles of some of these genes were discovered in our work at Stanford. A recent study showed that the test could predict which men had worse cancers.

How might this test impact patient care?  

These genetic tests could help identify men who harbor more aggressive cancers so that they can be treated. Perhaps more importantly, they might offer reassurance to men with non-life-threatening tumors that they can forego immediate treatment in favor of close observation - what we call "active surveillance." This way men can avoid the side-effects of treatment, and the genetic tests may help alleviate some uncertainty as to whether the cancer could be more aggressive than it appears.

Michael Claeys is the senior communications manager for the Stanford Cancer Institute.

Previously: Tackling the contentious issue of PSA testing, Ask Stanford Med: Answers to your questions on prostate cancer and the latest research and and To screen or not to screen? When it comes to prostate and breast cancers, that's still the question

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