Misleading Mammography Study Puts Women at Risk

When the British Medical Journal recently published an article that mistakenly concluded that annual mammography doesn’t save lives, news outlets like the New York Times jumped on the story—to the disservice of their readers.

The study was based on follow-up results of the Canadian Breast Cancer Screening Study (CNBSS), a five-year study conducted from 1980 to 1985. Responding to the journal article, the American College of Radiology and the Society of Breast Imaging stated:

“[The study] is an incredibly misleading analysis based on the deeply flawed and widely discredited CNBSS. The results of the British Medical Journal study, and others resulting from the CNBSS trial, should not be used to create breast cancer screening policy, as this would place a great many women at increased risk of dying unnecessarily from breast cancer.”

The CNBSS the study is flawed, according to experts. They found that mammograms obtained during the trial were of poor quality–even for 1980 to 1985–due to poor positioning and degraded images. Furthermore, contamination of the CNBSS control group also affected the results. Women underwent a clinical breast exam prior to assignment to the screening or control group. This likely resulted in an excess of women with palpable lumps in the screening arm, which led to more deaths in the screened population.

The Clear Benefits of Mammography

Many randomized controlled clinical trials have shown the benefit of mammography screenings. For example, the Swedish Two-County Trial, published in Radiology, reported a mortality reduction of 30 percent. Furthermore, a study published in Cancer Epidemiology, Biomarkers and Prevention showed that mammography screening cuts the risk of dying from breast cancer in half.

Other organizations that recommend women begin annual mammograms at age 40 include:

  • American Cancer Society
  • American College of Radiology
  • American Congress of Obstetricians and Gynecologists
  • National Accreditation Program for Breast Centers
  • Society of Breast Imaging

Constant improvements in medical-imaging quality make it easier to detect breast cancer early. In addition to digital mammography, we now have breast tomosynthesis, which decreases “recalls” from screening mammography and finds more cancers.

Arguments against screening mammography are bound to continue as long as we face unsustainable rising health care costs. Yet it is vital to finding cancer early, when it is most treatable. It not only saves lives but also helps preserve quality of life.

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