A new study in the New England Journal of Medicine says mammograms do not lead to better outcomes for women with breast cancer, and may actually lead to overdiagnosis of tumors that won't lead to cancer.
In all, perhaps 1 million women underwent treatment for tumors that weren't life-threatening, including chemotherapy and surgery, says the study. That's between 50,000 and 70,000 women every year.
The authors of the study compared rates of death from breast cancer now and thirty years ago. The number of mammograms has increased exponentially in the ensuing decades.
The American Cancer Society advocates yearly mammograms for all women over the age of 40.
While the number of breast cancer diagnoses doubled in the last thirty years, the number of deaths from breast cancer dropped only 8 percent. That likely means that the early screenings and detection aren't doing much to prevent deaths from the disease.
And in the meantime, tens of thousands of women are undergoing the emotional and physical trauma of a cancer diagnosis and its treatment when that cancer likely never would have become life-threatening.
The study's authors estimate that for every woman who is saved by early detection, three are overdiagnosed.
The study also found that the greatest decrease in deaths from breast cancer is in survivors under the age of 40, who never had mammograms, indicating that the decrease in the death rate stems from advances in treatment and not early screenings.
British studies have found similar results, and doctors are coming to the conclusion that they still have few ways to distinguish a benign lump from a cancerous tumor, especially when both are still tiny masses.
But it is becoming clear that mammograms may not be one of them.