Q. My husband and I are confused about the value of two screening tests that recently have been in the news -- mammography for me, and a PSA test for him. Should we or shouldn't we have these tests done on a routine basis?
A. Unfortunately, the answer for both of you is that "it depends." As I discussed in my July 30, 2011, column, the value of screening tests such as these is hotly debated. And let me explain why. All screening tests, such as mammography (to look for breast cancer in women) and the PSA, prostate-specific antigen, blood test (to look for prostate cancer in men) have to balance the risks of overdiagnosis (that is, saying that cancer is present when it is not, or what we call a false positive test result) and underdiagnosis (missing a cancer when it is, in fact, present, or a false negative test result). Both kinds of errors cause patients problems, by either having them falsely worried that they have cancer when they don't, or falsely reassured when they actually have something to worry about.
The problem with screening mammography, especially for younger women below 50 years of age, is that it often is falsely positive. A recent study found that over a 10-year period, more than half of younger women undergoing annual mammograms will have a false indication of possible breast cancer, and at least 7 percent will have a falsely positive breast biopsy. And mammography will "only" pick up a few cancers during that time. It turns out that about 1,900 younger women have to be screened to pick up one cancer. This concept is called the number needed to treat or NNT--that is, the number of people who have to get the "treatment" (in this case mammography) in order to have one patient benefit (in this case, be diagnosed with otherwise inapparent breast cancer).
Conversely, perhaps the main problem with the PSA test is that it often fails to identify patients with invasive or serious disease -- precisely what it was supposed to do. It turns out that prostate cancer becomes more common as men age, so that by 80 years of age most men have microscopic areas of cancer in their prostate, but are without any evidence of invasive disease. Most of these men will end up dying with their prostate cancer, rather than from it. So treating them almost certainly does more harm than good. The PSA test was devised to identify that smaller cohort of men who have aggressive prostate cancer and will die from, rather than with, the disease. But it turns out that the test can't separate the two groups very well, and thus a recent panel recommended against the routine use of the PSA test.
The current recommendations for breast and prostate cancer screening are highly controversial, and their use therefore needs to be individualized. So if you are under 50 years of age, I'd recommend mammography only if you and your health care provider feel that the benefits outweigh the risks. For most women, the answer will probably be "No." For your husband, unless he already has been diagnosed with prostate cancer (where the PSA test can help monitor the activity of the cancer), has symptoms, or is in a particularly high risk group (such as someone with a particularly bad family history of prostate cancer), the answer for your husband also is likely to be "No."
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Wynne is vice president for health affairs at UND, dean of the School of Medicine and Health Sciences, and a professor of medicine. He is a cardiologist by training.
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The content of this column is for informational purposes only and does not substitute for professional medical advice or care. The information provided herein should not be used for diagnosing or treating a health problem or disease. If you have or suspect you may have a health problem, you should consult your health care provider. Never disregard professional medical advice or delay in seeking it because of something you have read in this column.
