Two large studies question the value of routine mammograms, renewing debate over when to screen for breast cancer.

Two recent studies of the use of mammography as a breast cancer screening tool are prompting renewed debate about its value.

A recent analysis of 25 years of data from the Canadian National Breast Screening Study found that annual screening in women ages 40 to 59 did not reduce death rates from breast cancer any more than physical breast exams alone.

The study, published in the British journal BMJ, followed nearly 90,000 women who were randomized to receive either annual mammograms and breast exams for 5 years or breast exams alone. After 25 years, researchers found mortality rates were similar among the two groups, and that 22% of breast cancers detected through screening were over-diagnosed and would not have required treatment. The study's investigators believe modern care, including treatments like tamoxifen, has improved survival rates to the point that aggressive screening does more harm than good.

A second study published in the Annals of Internal Medicine shows that screening women ages 50 to 75 for breast cancer every 2 years, as recommended by the U.S. Preventive Services Task Force (USPSTF), would save $4.3 billion a year compared to current practices.

To compare the costs of screening approaches, investigators combined population data from the Breast Cancer Surveillance Consortium and other sources with Medicare reimbursement rates to model aggregate costs. They first modeled existing mammography practices in the U.S. to create a reference point. They then simulated three specific screening strategies: the American Cancer Society's preferred approach of annual mammograms for women ages 40 to 84; a European approach that calls for biennial screening in women ages 50 to 70; and the USPSTF's recommendation of biennial screening for women ages 50 and up, with higher-risk women starting screening at age 40.

The study estimates 70% of U.S. women are screened in a variety of ways—either annually, biennially, or irregularly—at a cost of approximately $7.8 billion per year. Assuming the participation rate was low for a variety of reasons, investigators compared the three screening strategies using an optimal target participation rate of 85%. “We chose 85% because that has been seen in cervical cancer screening and in mammography in European countries,” says lead author Cristina O'Donoghue, MD, MPH, of the University of Illinois Hospital in Chicago. At this rate, the model showed annual screening would cost about $10.1 billion per year, the European approach about $2.6 billion per year, and the USPSTF approach about $3.5 billion per year.

“The largest drivers of cost were screening frequency, percentage of women screened, cost of mammography, percentage of women screened with digital mammography, and percentage of recalls,” says O'Donoghue, adding that the use of Medicare reimbursement rates may underestimate the true costs, and that costs will likely rise with the use of new technologies.

The American College of Radiology and the Society of Breast Imaging responded to the studies, calling them “flawed” and “misleading.” The groups argue that the quality of the mammograms and the randomization process were not adequate in the Canadian study, and they dispute the savings in the economic model, saying that the costs of treating more advanced cancers, resulting from fewer mammograms, were not factored in. The groups point to a 2011 perspective in the American Journal of Roentgenology that concludes that bypassing annual screening starting at age 40 could result in up to 10,000 more deaths per year.

Investigators who created the economic model agree the study has limitations, but say that it's meant to start a discussion. “This study was not designed to ration screening but to understand how resources are currently being used,” says O'Donoghue, who believes more resources should be directed toward improving breast cancer risk assessment, genetic counseling, and improving the quality of mammography.