A recent study from the New England Journal of Medicine posits that more than half of abnormalities picked up by mammogram screenings — and treated with aggressive, anxiety-inducing procedures — will never become deadly. These findings cast doubt on the value of universal breast cancer screenings for women over the age of 40 who have no familial history of the disease, The Los Angeles Times reports.
The study examined data from the National Cancer Institute, tallying the number and size of tumors found in women over 40 between 1975 and 1979 — a time when screening mammography was not yet widely available. Those findings were then compared to similar data from 2000 to 2002, when preventative screenings had become routine. Researchers also tracked how the cancers were treated, and whether the patients were alive 10 years after their diagnoses.
Their results showed that breast cancer diagnoses increased as mammograms became more common. The cancers found tended to be smaller, and confined to areas like the milk ducts. But the rate at which mammograms detected large and aggressive tumors was largely unchanged between 1975 and 2010.
These findings, the study suggests, indicate that mammograms are not particularly effective at detecting dangerous tumors in their early stages. If treating tumors while they were still small was key to preventing the growth of aggressive tumors, widespread screening would have reduced the number of large tumors picked up by mammograms. In fact, researchers estimate that 80 percent of women who were treated for small lumps would have likely been fine without any intervention.
The number of deaths resulting from breast cancer have declined in recent years. But, after calculating changes in mortality rates among women diagnosed with tumors of varying sizes, researchers posited that this trend can be credited to better treatment methods—not earlier detection.
The study has received some pushback from the medical community. Small tumors can, in some cases, be biologically aggressive, and cancer is easier to treat if it is caught in its early stages. Dr. Kathryn Evers, director of mammography at Fox Chase Cancer Center in Philadelphia, told CBS News that mammograms are still the best way to find dangerous tumors that cannot be felt.
But the study nevertheless indicates a need for physicians to rethink the value of indiscriminate breast cancer screening. As Dr. Joann G. Elmore, a physician and epidemiologist at the University of Washington, wrote in an editorial accompanying the study: “The mantras, ‘All cancers are life-threatening’ and ‘When in doubt, cut it out,’ require revision.”
Read the full story at The Los Angeles Times.