A mammogram is an X-ray screening method that’s used for the detection of breast cancer. Confused about whether or not you need one? You’re not alone: In 2009 the US Preventive Services Task Force—an independent panel of health providers that makes recommendations on health services, including screenings—recommended that women ages 50 to 74 have a mammogram every other year. The American Cancer Society, on the other hand, recommends yearly mammograms for women 40 and up.

But now two recent studies suggest that mammograms may not offer much benefit at all: One analysis of 450 studies concluded that the benefits were "modest," while the risks were "significant." And a large Canadian study (which followed nearly 90,000 women for 25 years) found that women who received annual mammograms died of breast cancer at similar rates as women who had annual clinical breast exams. Furthermore, many women who received mammograms underwent unnecessary treatment.

Understanding the Findings

This debate isn’t about the value of early detection for breast cancer; it’s about the value of different types of detection.

H. Gilbert Welch—an MD, MPH, professor of medicine at Dartmouth Institute for Health Policy and Clinical Practice, and the author of Should I Be Tested for Cancer? Maybe Not and Here's Why—says the way the Canadian study was conducted is significant: Most mammogram studies compare women who have regular mammograms with women who don’t.

But in the Canadian study, participants aged 50-59 were randomly assigned to receive either annual clinical breast exams by specially trained nurses, or annual clinical breast exams plus mammograms, which are designed "to detect abnormalities that are too small to feel," as Welch put it in an article on CNN.com. But finding these "abnormalities doesn't help women live longer," since the study determined that the women who received annual mammograms died of breast cancer at similar rates as women who just had annual clinical breast exams.

Concerns About Overtreatment

Because common cancer treatments—like chemotherapy, radiation, and surgery—carry risks and can cause significant side effects, medical experts like Welch worry about overtreatment. Small cancers that are not likely to grow significantly, or may not require treatment at all, are treated at high rates—because oncologists (doctors who specialize in treating cancers) can't tell which small tumors will become dangerous, they treat them all. Welch says researchers believe even invasive cancers are overdiagnosed and overtreated.

Next Steps for You

So what should women do in the face of all the conflicting recommendations about if, when, and how often to undergo screening mammography?

The answer? Be a proactive healthcare consumer. Understand the benefits and risks of mammograms, and what mammography realistically can—and cannot—do. Discuss your risk factors, such as your age and family history, with your physician. Also consider your risk tolerance, or how comfortable you might be with an ambiguous finding. If you follow these guidelines, you and your doctor will be able to make breast cancer screening decisions that are right for you.

Rajiv Datta, MD, Chair, Department of Surgery, Director of the Division of Surgical Oncology and Head and Neck Surgery, and Medical Director of Gertrude and Louis Feil Cancer Center at South Nassau Communities Hospital in Oceanside, NY, reviewed this article.


Lydia E. Pace, Nancy L. Keating. "A Systematic Assessment of Benefits and Risks to Guide Breast Cancer Screening Decisions." JAMA. 2014; 311(13): 1327-1335. doi:10.1001/jama.2014.1398. 

Susan Silberstein. "To Screen or Not to Screen: The Mammogram Conundrum." BeatCancer.org. Accessed April 21, 2014. 

"Twenty Five Year Follow-Up for Breast Cancer Incidence and Mortality of the Canadian National Breast Screening Study: Randomised Screening Trial." BMJ 2014; 348 doi: http://dx.doi.org/10.1136/bmj.g366, published February 11, 2014. 

Gayle Sulik and Bonnie Spanier. "Time to Debunk the Mammography Myth." CNN.com. March 18, 2014. 

H. Gilbert Welch. "Don't Slam Canada for Mammogram Study." CNN.com. February 19, 2014. 

Denise Grady. "Look for Cancer, and Find It," NYTimes.com. April 7, 2014.

"Screening for Breast Cancer." U.S. Preventive Services Task Force. Page updated December 2009. 

"American Cancer Society Guidelines for the Early Detection of Cancer." American Cancer Society. Page last revised May 5, 2013. 

Nick Mulcahy, "JAMA Review: Stop One-Size-Fits-All Mammography." Medscape.com. April 2, 2014. 

Welch, Gilbert H. Should You Be Tested for Cancer? Maybe Not and Here’s Why. Berkeley and Los Angeles: California, University of California Press, 2004.