Are Breast Cancers Over Diagnosed?

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Researcher Karsten Juhl Jørgensen feels that breast cancers are over diagnosed. He begin his review of incidence reported data from 7 years before routine screening programs were implemented and 7 years after full screening was implemented. He included screened and non-screened age groups. Data was available from United Kingdom; Manitoba, Canada; New South Wales, Australia; Sweden; and parts of Norway.

Jorgensen’s objective was to estimate the extent of over diagnosis. The working definition of over diagnosed breast cancers is “the detection of cancers that will not cause death or symptoms.”

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The results of Jorgensen’s systematic review is published online in the July 9th issue of British Medical Journal. His review shows an estimated 52% over diagnosis of breast cancer.

Looking at the United Kingdom data, he found that the screening program began in 1988 for women aged 50-64. National coverage began by 1990. The screening was expanded to women aged 65-70 in 2002. There was a 41% higher than expected rate of invasive cancer found in women aged 50-64 during the 1993-1999 period with no compensatory drop during the 7 yrs after full screening was implemented. This is interpreted as over diagnosis of breast cancer.

This same trend was found in the data from the other countries. Combining the data, the researchers estimated 52% over diagnosis of breast cancer in a populations of women who are offered organized mammography screening. That amounts to one in three breast cancers being over diagnosed.

Source
Overdiagnosis in publicly organised mammography screening programmes: systematic review of incidence trends; BMJ 2009;339:b2587; Karsten Juhl Jørgensen, researcher, Peter C Gøtzsche, director

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