HEALTH MATTERS: Benefits of screening mammography for women in their 40s are modestQ. I am a 43-year-old woman, and I’m trying to decide whether I should undergo a yearly mammogram. My gynecologist just told me that her national organization recommends this, but I recall that a national panel did not. What should I do?
By: Dr. Joshua Wynne, Grand Forks Herald
Q. I am a 43-year-old woman, and I’m trying to decide whether I should undergo a yearly mammogram. My gynecologist just told me that her national organization recommends this, but I recall that a national panel did not. What should I do?
A. Mammography is unquestionably the most carefully studied screening test in medicine. No other test has been as closely studied as mammography regarding its effect on reducing early death from cancer. Despite this, the indications for, and benefits of, screening mammography, especially for women like you who are in their 40s, are among the more disputed in all of medicine.
As you note, the American College of Obstetricians and Gynecologists just last week recommended yearly mammograms for women in their 40s, while the U.S. Preventive Services Task Force report from about two years ago did not.
Why the difference in recommendations? It’s mainly because of the imperfect nature of any screening test. The benefit of a screening test like mammography is a function of three variables: the risk of the underlying condition (in this case, breast cancer) if undiagnosed and untreated; the effectiveness of the screening test in identifying disease that can be treated; and the risk of harm from the screening test (including the risk of radiation itself from the mammogram and also the risk of breast biopsies and other treatment).
Women in their 40s have a much lower risk of breast cancer than older women, so the value of screening is less. And mammography does not catch all of the breast cancers. Finally, mammography falsely identifies breast cancer in many women in their 40s and 50s, so there is some harm associated with screening.
To make these ideas clearer, consider the following: For women in their 40s, to prevent one death from breast cancer for a 10-year period, about 2,000 women would need to be screened. Even for a 50-year-old woman (where the risk of breast cancer is higher), the chance of developing breast cancer in the ensuing decade is “only” about four per 1,000 women.
If one uses the most optimistic estimates of the effectiveness of screening, the risk of breast cancer with no screening “only” goes up to about five per 1,000 women. But the “cost” of screening would be that 500 to 1,000 women would have a “false alarm,” (a false positive test result that suggests breast cancer where none exists) and about half of these women would undergo a biopsy (an invasive procedure) that would show the mammography result was incorrect. Looking at it from the opposite perspective, adding screening mammography for women in their 40s increases the number of women who will not die of breast cancer during a 10-year period from about 995 to 996 per 1,000 women.
Thus, it is probably fair to say that the benefits of screening mammography for women in their 40s are modest and are balanced by modest risks. The “correct” use of mammography in this setting clearly is in a gray area, where one needs to try to balance the benefits against the risk.
By contrast, it seems clear that the benefits of screening mammography for women in their 60s more than outweigh the risks, just as it is clear that the risks of screening mammography for most women in their 30s outweighs any possible benefits. But for women like you who are in their 40s, there is no easy answer. In this setting, the best advice I have is to discuss the matter with your health care provider, and make the decision that feels most comfortable to you.
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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