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Commentary: Why Yearly Mammograms Can Be Harmful

A woman undergoes a mammogram at Mt. Sinai Hospital in Chicago. Photo by Heather Charles/Chicago Tribune/MCT via Getty Images.

In the last 30 years, mammograms have led 1.3 million women to seek treatment for cancer that would never have harmed them, according to a recent report in the New England Journal of Medicine. “At best,” the report says, mammograms have had “a small effect on the rate of death from breast cancer.”

It’s an assertion the American College of Radiology and other prominent groups call “flawed and misleading”, adding that it could confuse women who should be receiving the test and cost lives. On Tuesday evening’s PBS NewsHour broadcast, health correspondent Betty Ann Bowser explores this latest firestorm in the oncology community and what ordinary women should take away from all of the conflicting information.

In the meantime, we’ve asked three of the nation’s most influential doctors whether women over the age of 40 should be screened yearly. Dr. Sandra Swain of the American Society of Clinical Oncology says yes. Below, Dr. Archie Bleyer, co-author of the New England Journal of Medicine report, says no. And Dr. Barnett Kramer, director of the National Cancer Institute’s Division of Cancer Prevention, explains the scientific basis for both arguments.

Dr. Archie Bleyer is a clinical research professor in the Knight Cancer Institute at the Oregon Health and Science University and a professor of pediatrics at the University of Texas Medical School at Houston. He co-authored the recent study in the New England Journal of Medicine titled, “Effect of Three Decades of Screening Mammography on Breast-Cancer Incidence.”

Dr. Archie Bleyer: For 30 years women in the U.S. have been told to get a mammogram (X-ray of breasts) every year after the age of 40. Three years ago, a group of experts in prevention and evidence-based medicine commissioned by our government and including internists, family physicians, gynecologists, nurses, and health behavior specialists (known as the U.S. Preventive Services Task Force) reviewed this policy and recommended a reduction in the amount of screening mammography in women who are not at increased risk of breast cancer. Instead of the then standard 40 to 50 scans depending on the woman’s natural lifespan, they recommended 13 scans between age 50 and 75 at every-other-year intervals.

This recommendation was contested, especially by mammographers, oncologists and breast cancer advocacy organizations. The controversy continued with more studies attempting to better define the extent to which screening mammography reduced deaths from breast cancer. None of these studies looked at the first effect any screening procedure must achieve before it can reduce deaths: a substantial increase in the detection of early-stage disease that results in a comparable reduction in late-stage disease.

To save lives, a cancer screening test must both increase early-stage and decrease late-stage cancers that are found, demonstrating its ability to advance the time of diagnosis to an earlier time and stage. Unless late-stage cancer is reduced, any observed reduction in cancer deaths must be due to something else.

Our study differed from the others by looking for this prerequisite effect in the U.S. After correcting for underlying trends and the use of hormone replacement therapy, we found that the introduction of screening has been associated with about 1.5 million additional women having been diagnosed with early-stage breast cancer. That would be outstanding if it meant that 1.5 million fewer women had been diagnosed with late-stage breast cancer. We could then conclude that screening had indeed advanced the time of diagnosis and provided the opportunity of fewer deaths and/or less therapy for 1.5 million women.

Instead and disappointingly, we found that there were only about 140,000 fewer women with a diagnosis of late-stage breast cancer. The discrepancy between 1,500,000 and 140,000 meant that more than 1.3 million women were told they had early-stage cancer and underwent surgery or surgery with radiation, years of hormone therapy, and in some, chemotherapy for a “cancer” that if they had done nothing was never going affect them.

Even worse was the finding that metastatic breast cancer, the kind that has by far the worst survival, appeared to have had no benefit at all. Other countries have reported similar rates of overdiagnosis, which is what the discrepancy is called, but the number of women affected in the U.S. is greater because our population, years we have been screening, percentage of women screened, and the years of their life screened have been greater.

Unfortunately, we can’t tell which women are overdiagnosed. So until healthcare finds a more effective way to screen for and diagnose cancer, what should a woman do if she is about to reach the age of 40 or is currently getting annual mammograms.

The first step is to be more informed about the potential harms of screening mammography. These include anxiety (likely made worse with our report), procedures, costs, and now the additional concern that overdiagnosis is a greater problem than previously appreciated. A YouTube video about our study can help understand the problem:

A second step is to discuss screening mammography with one’s doctor, as the new guidelines recommend. If the doctor is reluctant to advise because of the controversy, a primary care provider or more informed physician who understands prevention practices should be consulted.

A third effort is to resist being harassed into being screened. Each woman and her doctor should know that she really has a choice and can decide for herself about the benefit and harms.

Doctors can also do better. They can look less hard for tiny precancers and put more effort into differentiating between consequential and inconsequential findings. Ultimately, they must either redesign screening protocols to reduce overdiagnosis or stop population-wide screening. They can stop using screening mammography as a public health imperative or measure of the quality of our health care system.

There is also good news from our study. If screening is saving fewer lives than we thought, then treatment can be given more credit for the remarkable progress we have made in reducing breast cancer deaths. Future breast cancer patients can be reassured that treatment is even better than we realized.

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Headshot photo courtesy of St. Charles Health System.

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