“Effect of three decades of screening mammography on breast-cancer incidence.” By A. Bleyer and H.G. Welch, New England Journal of Medicine

A study published in the New England Journal of Medicine concludes that one-third of all newly diagnosed breast cancers are the result of overdiagnosis, and screening is having a marginal effect on the breast cancer death rate. Examine trends from 1976 through 2008, the researchers found that despite substantial increases in the number early-stage breast cancers (ductal carcinoma in situ and localized disease) in the United States, screening mammography has only marginally reduced the rate at which women present with advanced cancer (regional and distant disease). An effective screening program would both increase the incidence of cancer detected at an early stage and decrease the incidence of cancer presenting at a late stage. The imbalance suggests that there is substantial overdiagnosis (detecting cancers that would never become life-threatening or cause symptoms), accounting for nearly one-third of newly diagnosed breast cancers (more than 70,000 women).

One of the researchers, Archie Bleyer, MD, of Oregon Health and Science University in Portland, told MedPage Today that breast cancer mortality has been falling in the U.S., a decline usually attributed to a combination of increased screening and better treatment. The study implies, he said, that “treatment … is the main, if not the only, reason for the improvement” in survival.

Source: Bleyer A and Welch HG. “Effect of three decades of screening mammography on breast-cancer incidence.” New England Journal of Medicine 2012; 367: 1998-2005.

Related Article: Zalman, A. “Study Suggests Breast Cancer Overdiagnosed.” Medpage Today (Nov. 21).

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