Their results are based on 100,000 women aged 50 and older surviving up to 20 years after they started screening.
When the researchers included data on false positive tests and unnecessary surgery, the benefits of screening were cut in half.
Their best estimates found a negative quality of life measurement for up to eight years after screening, and only modest gains after 10 years.
After 20 years, the quality of life benefits improved, but much less than the Forrest Report had predicted, they found.
"From a public perspective, the meaning and implications of overdiagnosis and overtreatment need to be much better explained and communicated to any woman considering screening," the researchers concluded.
Dr. Julie Gralow, director of breast medical oncology at the University of Washington in Seattle, disagreed strongly with the new study findings.
"The cumulative evidence from randomized clinical trials shows the screening mammograms reduce deaths due to breast cancer," she said. "This is objective fact."
The effects of the harms of a false positive mammogram are very subjective, Gralow added. "A call-back for additional views is expected in a certain percentage of women; many times the extra images are enough to resolve the problem without a biopsy," she said.
"If you want to catch as many cancers at an early stage as possible, you have to follow up on anything of moderate suspicion. Many women understand this and accept it," Gralow said.
A biopsy, which is rarely done surgically any more, that shows benign disease has the potential for some psychological harm, Gralow acknowledged. "But it can't possibly be weighed equally or even close to equally against saving a life," she said.
"For many women surgery for a low-risk breast cancer is just not a big deal," she added. "I'd equate surgery for low-risk breast cancer with removing a colon polyp. It may or may not cause trouble if not
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