"Many experts agree that there is some degree of overdiagnosis and overtreatment," said Dr. Len Lichtenfeld, deputy chief medical officer of the American Cancer Society. However, "you can't have a significant decline in mortality unless you're doing something right," he added. "I think it is a combination of mammography, increased awareness and better treatment."
Lichtenfeld added that it is very difficult to assess how much mammography, on its own, is contributing to reductions in breast cancer deaths.
The true overdiagnosis rate in the United States is difficult to know because it can vary based on how researchers analyze the numbers, Lichtenfeld noted.
"Today's paper says that mammography has limited benefit, but tomorrow's paper may say that it has significant benefit," he said.
Amid all this, the American Cancer Society continues to recommend that women get annual mammograms starting at 40 years of age, Lichtenfeld said.
For his part, Bleyer thinks that women should get mammograms every other year between the ages of 50 and 70, similar to controversial guidelines issued by the U.S. Preventive Services Task Force in 2009.
Even though Bleyer's study did not find a decrease in the cases of distant disease, it estimated that the rate of regional disease decreased by 8 percent. Regional disease is a form of late-stage cancer, but unlike distant disease, it has only spread within the area of the breasts, usually the lymph nodes, and is more treatable.
To estimate the rate of overdiagnosis, Bleyer and his colleague used U.S. data from between 1976 and 2008 on breast cancer incidence and survival rates from the Surveillance, Epidemiology, and End Results (SEER) program. They also relied on survey data estimating how many women get mammograms.
The researchers found that incidence of early-stage breast cancer increased between the mid-1980s and 2000 among women 40 years
All rights reserved