Researchers question efficacy of mammograms

Just in time for Breast Cancer Awareness Month, a new medical study suggests mammograms might be less effective than previously thought.

But before you go cancelling that mammogram, know that local doctors take issue with that conclusion, which is similar to the findings of a few other studies conducted during the last decade.

The most recent study, published in The New England Journal of Medicine, looked at how diagnosis numbers changed between 1975 — before mammography was widespread — and 2012. The Dartmouth College researchers used data from women age 40 and over who took part in a national cancer case-tracking program.

Researchers found after mammogram screenings became widespread in the 1980s, incidence of small tumors almost doubled. Meanwhile, incidence of larger tumors showed a slight decrease. The rate of metastatic cancer – the most fatal type of cancer – remained unchanged.

The findings gave researchers pause because, if mammograms were effectively catching smaller tumors before they grew larger, the incidence of larger tumors would have dropped a lot more significantly, they said.

Instead, the researchers suspect mammograms often catch small tumors that are unlikely to grow larger and manifest cancer symptoms. Analysis showed about 80 percent of the additional small tumors detected wouldn’t have grown to be more dangerous.

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The findings describe what some scientists call “overdiagnosis” of cancer.

Local breast cancer doctors warn women against using the study to make a judgment on mammography. Larimer County's breast cancer rate is about 129 new  cases per year for every 100,000 people, slightly higher than incidence in the rest of the state, according to State Cancer Profiles data. Breast cancer killed 341 people in Larimer County between 2002 and 2012 and accounted for about 18 percent of cancer diagnoses, the second-most of all cancer types.

“The estimates of overdiagnosis are based primarily on conjecture and personal opinion,” wrote Dr. Jean Paquelet, a radiologist and breast imager at Advanced Medical Imaging Consultants and UCHealth Breast Diagnostic Center, in an email to the Coloradoan. “There actually is no hard evidence of significant overdiagnosis of breast cancer.”

Dr. Deborah Gunderson, medical director of UCHealth Breast Diagnostic Center and a radiologist at Advanced Medical Imaging Consultants, added treatment of smaller breast cancers generally calls for less extensive surgery and less chemotherapy. Mammography can't by itself predict which breast cancers will be aggressive, she wrote in an email to the Coloradoan.

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“We use mammography to detect cancers when they are small, knowing that some will not cause loss of years lived, but also knowing that we are catching the aggressive breast cancers when they have the best chance for good outcome with treatment,” she wrote.

Several national cancer research and prevention groups agree that the most lives are saved by annual screenings beginning at age 40. You can find research in support of mammograms at mammographysaveslives.org.

And regardless of where you stand on mammograms, the story has a silver lining: The breast cancer death rate has dropped by more than one-third since mammography became widespread.