Swedish Mammography Study Shows Screening Reduces Mortality

A prospective case-control study from Sweden has found long-term benefits of regular mammography screening, including a positive impact on reducing mortality.

Dr Lszl Tabr, medical director of the department of mammography at Falun Central Hospital and professor of radiology at the University of Uppsala School of Medicine in Sweden, and colleagues conducted a 29-year study in which they followed 133,065 women aged 40 to 74 years; the women resided in 1 of 2 Swedish counties. The women received either an invitation for mammographic screening or usual care. Local end point committees and independent external committees determined case status and cause of death, when necessary. Negative binomial regression was performed as part of the mortality analysis.

A highly significant reduction was found in breast cancer death for those patients invited to screening (relative risk = 0.69; P < 0.0001). According to the local data, 414 women were needed to undergo screening for 7 years to prevent 1 breast cancer death. After 29 years of follow-up, the researchers found that approximately 414 women needed to undergo screening every 2 or 3 years over a 7-year period to prevent 1 breast cancer death.

In a statement to the press, Stephen W. Duffy, professor of cancer screening at Queen Mary, University of London, explained: "Most of the deaths prevented would have occurred more than 10 years after the screening started. This indicates that the long-term benefits of screening in terms of deaths prevented are more than double those often quoted for short-term follow-up." Duffy also noted that the data further emphasized the importance of regular mammography screening.

"Unfortunately, we cannot know for certain who will and who will not develop breast cancer," Duffy told the press. "But if you undergo a recommended screening regimen, and you are diagnosed with breast cancer at an early stage, chances are very good that it will be successfully treated."

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References

Tabár L, Vitak B, Chen TH et al. Swedish two-county trial: Impact of mammographic screening on breast cancer mortality during 3 decades.Radiology. June, 28, 2011 [Epub].
Press release. Study finds mammography screening reduces breast cancer mortality. Radiological Society of North America. June 28, 2011.