NCPA - National Center for Policy Analysis

Controversial Study Questions Value Of Mammograms

January 12, 2000

Danish researchers claim that mammography, one of the most widely used screening tests for breast cancer, may not reduce deaths from the disease.

"There is no reliable evidence that screening decreases breast cancer mortality," say Peter Gotzsche and Ole Olsen of the Nordic Cochrane Center in Copenhagen, Denmark, in Lancet, a British medical journal.

  • A 1999 study from Sweden found no decrease in breast-cancer mortality in Sweden, where screening has been recommended since 1985, whereas the expected decrease was 11 percent.
  • Gotzsche and Olsen re-examined the Swedish study, and seven other previously published trials that randomly assigned women either for mammographic screening or to an unscreened control group.
  • Six of those trials found that mammography decreased the risk of death by about 25 percent while two showed no significant effect.
  • But the scientists said only those two -- conducted in Canada and the Swedish city of Malmo -- met widely accepted criteria for an adequate randomization process.

Other experts disagree, according to news reports. "Although the issue focused on by Gotzsche and Olsen is very important, they have disregarded the fact that other factors probably have a more important part in lowering the mortality rate than screening," says Harry de Koning of the Rotterdam Department of Public Health.

And Britain's Department of Health said there was "no new evidence" in the report by the Danish researchers. "The data has already been considered by expert committees on breast screening who found significant beneficial effects from screening women for breast cancer," it said in a statement.

Source: Peter C Gotzsche, Ole Olsen, "Is screening for breast cancer with mammography justifiable?," Lancet, January 8, 2000; Reuters, "Study questions value of mammograms, conclusion controversial," MSNBC.COM, Jan. 6, 2000.


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