BMJ: Breast cancer screening may not impact mortalilty

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A Danish study published yesterday online in the British Medical Journal questions whether breast cancer screening program can reduce breast cancer deaths.

Karsten J. Jørgensen, MD, and Peter C. Gøtzsche, MD from the Nordic Cochrane Centre in Copenhagen, as well as Per-Henrik Zahl, MD, PhD, from the Folkehelseinstituttet in Oslo, said they were responding to what they considered to be analytical problems with an earlier study that had attributed a 25 percent reduction in breast cancer mortality to breast cancer screening.

In this study, the authors compared annual changes in breast cancer deaths in two Danish locations—Copenhagen and Funen County—that had organized screening programs and compared them to non-screened regions across Denmark. For comparison purposes, the authors used data on breast cancer mortality from 1971 to 2006 retrieved from the Danish National Board of Health.

The authors divided the mortality data into three age groups: Women aged 55-74 years, who could benefit from screening, and women aged 35-55 years and 75-84 years, who were largely unaffected by screening.

In the group aged 55-74, breast cancer mortality declined by 1 percent a year in the screened areas and by 2 percent in the non-screened areas. In the 35-55 group, the breast cancer mortality rate declined by 5 percent a year in the screened areas and by 6 percent a year in the on-screened areas.

The authors found no significant changes in breast cancer mortality trends among women aged 75-84 years in either the screened or non-screened areas.

"We were unable to find an effect of the Danish screening program on breast cancer mortality," concluded the authors. "The reductions in breast cancer mortality we observed in screening regions were similar or less than those in non-screened areas and in younger age groups, and are more likely explained by changes in risk factors and improved treatment than by screening mammography."

"Our results are similar to what has been observed in other countries with nationally organized programs. We believe it is time to question whether screening has delivered the promised effect on breast cancer mortality," they wrote.