Mammograms: Not all they're cracked up to be?

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For many years, women have been urged, cajoled, brow-beaten even, to be sure to get their annual mammogram. Starting shortly after puberty s arrival and breast development, young women get the word: the annual mammogram is necessary to save your life!

Now, a new study of the likely benefits of screening mammograms shows that the large majority of abnormalities found turn out to be non-threatening lesions that would be better left undetected and undisturbed. In other words, most biopsies and lumpectomies provoked by routine screening X-rays are cases of what epidemiologists call overdiagnosis. This occurs when an indolent or benign growth is called cancer, although it s not going to progress, invade, spread, or otherwise pose a serious health threat.

It is undeniable that breast cancer survival rates have declined in recent years, and many women and their doctors believe this is due to earlier detection from screening mammograms. The study authors maintain that this effect is largely due to improved treatments, both surgical and medical, rather than detection benefits. It is also true that women who have clinical abnormalities, such as a lump or skin or nipple changes, or have a strong family history of breast cancer, should not be skipping mammograms. But those are not screening tests, but rather diagnostic exams for clear indications. Screenings are done routinely every year or so without specific reason.

The conclusions and recommendations of the new study apply to those screening tests only. The authors state that if such mammograms actually saved lives by preventing progressive, life threatening cancers, than late-stage cancers would also be in decline at least as much as the early-stage tumors and they are not.

The co-author of the study, Dr. H. Gilbert Welch, professor of epidemiology and biostatistics at the Dartmouth College School of Medicine, had this to say: Our study raises serious questions about the value of screening mammography. It clarifies that the benefit of mortality reduction is probably smaller, and the harm of overdiagnosis probably larger, than has been previously recognized. These harms include repeated medical testing, sonograms, MRIs, biopsies and lumpectomies, and the often-needless anxiety of being told of a diagnosis of cancer, when in fact the abnormality detected is not life-threatening.

The study used data from the US Centers for Disease Control and Prevention survey and from the American Cancer Society database. These analyses showed that since the general recommendation for all women over 40 to have screening mammograms in the late 1970s, and 2008, early-stage breast cancers doubled in frequency, while late-stage cancers decreased only by only 8 percent. This led the authors to conclude that millions of women have been diagnosed with cancer for no benefit to their long-term health indeed, to their detriment. A similar controversy, nearly a firestorm, occurred in 2009, when a federal advisory panel recommended that women under 40 were more likely to be harmed than benefitted by routine screening mammography, and that those 50 and over need only consider mammograms every other year, not annually.

The issue is not so cut-and-dried, however. Len Lichtenfeld, deputy chief medical officer of the American Cancer Society, said the society continues to recommend that women get annual mammograms starting at 40 years of age. Many experts agree that there is some degree of overdiagnosis and overtreatment, Lichtenfeld commented, adding however that you can t have a significant decline in mortality unless you re doing something right.

At the end of the day, the decision to have mammography routinely, and if so how often, is one that must be made by each woman, after thorough discussion of the likely benefits and risks with her physician, and maybe also with her family. But those who make women feel guilty about skipping the test, or who assert that mammograms are the best way to protect health, have less support now than they did before.

By ACSH's Dr. Gilbert Ross, M.D. Originally posted Nov. 25, 2012 on