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EDITORIAL: New Breast Screening Recommendations

  • November 18, 2009
  • Number of views: 3711
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By Barbara Monsees, MD
Ronald and Hanna Evens Professor of Women’s Health
Chief, Breast Imaging, Mallinckrodt Institute of Radiology and Siteman Cancer Center

Published this week in the Annals of Internal Medicine are several articles and an editorial dealing with the breast cancer screening recommendations of the U.S. Preventive Services Task Force. The general purpose of their efforts is a good one, to take an unbiased look at all the evidence and make recommendations based on science.

This task force looked specifically at the benefits and harms of breast cancer screening including mammography, digital mammography, magnetic resonance imaging, breast self examination and clinical breast examination.

In this type of process, they attempt to balance the pros against the cons, the benefits against the harms. The benefit is measured by the efficacy in reducing the death rate from breast cancer.  The harms included factors such as discomfort from mammography, anxiety from recall, ultrasound, and needle biopsy.  What is getting so much attention is the recommendations for mammography screening, and in particular, for women under the age of 50.

Despite controversy in the past, there is now universal agreement that screening mammography saves lives. That is not in question.

There is disagreement, however, in the estimates of how many lives are saved by screening and whether the benefits outweigh the risks at different ages.  The task force made estimates of the lives saved by screening for different age groups and balanced that against the so-called harms for that age group.  They then made a judgment call as to whether the lives saved in each age group is enough to justify a recommendation for routine screening in that age group.

It is incredibly important that they use the most accurate estimate of how many lives would be saved, because in weighing the benefits and the harms, this will be key to appropriate decision making. The task force used an estimate of about 15% reduction in breast cancer deaths for women in their 40’s, 14% for women in their 50’s, and 32% for screening women in their 60’s. They derived their estimates, however, only from randomized trials. These trials were important in validation that mammography indeed saves lives, but for a variety of reasons such trials underestimate the benefit of screening. Individual trials of women in their 40’s showed greater benefit, but when all the trials were combined in a meta-analysis, including both the better and more poorly conducted trials, the benefit may have been diminished by the process of the combination of trials. The task force excluded other types of data that shows a much greater benefit from mammography. For example, when mammography screening was introduced in Sweden, the death rate from breast cancer was reduced by about 40%.

In the U.S., the breast cancer death rate has decreased by 30% since 1990, when screening mammography began to be widely used.  Before that, the breast cancer death rate had been unchanged for the preceding 50 years.  These recent improvements are felt to be primarily due to screening mammography, although there has been some impact from newer therapies.

So in this balance of the benefits and the harms of mammography, I believe that the task force underestimated the benefit of screening with mammography. In addition, I believe the task force was overly concerned with the harms of screening.

Surveys have shown that the public understands that screening methods such as mammography are not perfect, and the public is willing to accept minor inconveniences in order to maximize the opportunity of finding a cancer earlier by screening.

The task force is recommending against routine screening mammography in women 40-49, suggesting that the decision be an individual one based on risk factors and the patient’s preferences on benefits and harms.  However, the fact is that most women who develop breast cancer in their forties do not have risk factors that might signal their doctors that they should be screened. Of women who die of breast cancer, 17% are diagnosed in their 40’s.  Forty percent of the years of life lost to breast cancer are from women who are diagnosed in their 40’s.  This makes sense because if a younger woman dies a premature death from breast cancer, she loses more years of her life than an older woman would have lost.

The task force also commissioned computer modeling methods, to simulate screening beginning and ending at different ages, and with screening yearly and every other year.  The task force is recommending that women begin screening at age 50 and be screened every two years until age 74. I believe that screening should be done yearly to catch more of the faster growing tumors.

The task force said that there was insufficient data for them to make a recommendation for women aged 75 or older. That is because only two randomized trials included women over the age of 69.  However, I’d like to point out that a healthy woman at age 75 has many years of life to live. While there is no proof that mammography saves lives at that age, there is no reason to believe that it would not.  It just has not been tested.

The task force could not find enough information to make any recommendation on digital mammography or magnetic resonance imaging of the breasts. It is also recommending against breast self examination, and says that it has insufficient data to recommend clinical breast examination.

It should be pointed out that even if regular self breast examination is not recommended, a woman should be familiar with her body. If she finds a lump or another sign of cancer, she should bring that to the attention of her physician, even if she had a recent negative mammogram.  Additional imaging is usually warranted in such situations, since mammography, like other screening tests is far from perfect.

The American Cancer Society uses all available evidence in making its screening recommendations. They include trends in mortality and other publications, not just published randomized controlled trials. I endorse the recommendations of the American Cancer Society which recommends yearly mammography screening beginning at age 40, to continue as long as a woman is in good health.

It is a good idea that women should speak to their physicians if they have a strong family history of breast and/or ovarian cancer, since such women may also benefit from supplemental screening with MR.

Medicare and third party payors often use the USPSTF recommendations in deciding on payment for medical services.  I worry that if insurers cut screening benefits, this will result in fewer women screened regularly and an increase in the breast cancer death rate.

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