Are breast cancers over-diagnosed? If so, how often? Those are the questions looked at by the systematic review of incidence reported data/articles done by Karsten Juhl Jørgensen & colleagues. Their results are published online in the June 9th issue of the British Medical Journal. Their review shows an estimated 52% over-diagnosis of breast cancer.
The researchers’ objective was to estimate the extent of over-diagnosis. Screening for breast cancer is meant to detect lethal cancers earlier. Unfortunately it also detects harmless ones that will not cause death or symptoms. As it is not possible to distinguish between lethal and harmless cancers, all detected cancers are treated. Over-diagnosis and overtreatment are therefore inevitable.
They begin their review of incidence reported data from 7 years before routine screening programs were implemented and 7 years after full screening was implemented. They included screened and non-screened age groups. Data was available from United Kingdom; Manitoba, Canada; New South Wales, Australia; Sweden; and parts of Norway.
This data came from a PubMed search (May 2006) which yielded 2861 titles, 2546 of which were not relevant. That left 315 articles which were evaluated. Four were included as core articles and one was added when the search was updated in April 2007, presenting data from the United Kingdom; Manitoba, Canada; New South Wales, Australia; Sweden; and parts of Norway. A meta analysis was done on the data.
Looking at the United Kingdom data, they 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 chart (photo credit) shows the incidence of invasive breast cancer per 100,000 women in UK.
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.
We need improved screening methods to decrease this number to less than 10% over-diagnosis. Each “un-necessary” surgery for one of the over-diagnosed cancers puts the patient at risk for complications. Not to mention the increased cost to the healthcare system of each country.
Overdiagnosis in publicly organised mammography screening programmes: systematic review of incidence trends; BMJ 2009;339:b2587; Karsten Juhl Jørgensen, researcher, Peter C Gøtzsche, director
A Few Other Breast Cancer Related Posts
Breast Self Exam (BSE) (October 2008)
Mammograms (October 2008)
Breast Cancer Screen in Childhood Cancer Survivors – An Article Review (February 2009)
Indications for Breast MRI – an Article Review (March 2009)