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21-03-2013 | Legal medicine | Article

Dispute over biannual breast screening

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medwireNews: Screening women aged 50 to 74 years old for breast cancer every 2 years is as effective as annual screening but reduces the rate of false-positive diagnoses, conclude the authors of a US study.

Furthermore, regardless of breast density or hormonal therapy use, women screened biennially who were diagnosed with breast cancer were at no greater risk for unfavorable tumor characteristics than women screened annually.

The findings support the 2009 recommendation of the US Preventive Services Task Force that screening intervals in this age group be extended from 1 to 2 years, say Karla Kerlikowske (University of California, San Francisco) and colleagues in JAMA Internal Medicine.

"For women 50 to 74 years old with dense breasts who are cancer free, we estimated that more than half will be recalled for additional mammography at least once over the course of 10 years of annual screening," said study co-author Rebecca Hubbard (Group Health Cooperative, Seattle, Washington) in a press statement. "Screening every other year decreases this risk by about a third."

In the study of 11,747 women with breast cancer, those aged 50-74 years old with heterogeneously or extremely dense breasts receiving combination hormonal therapy were no more likely to have advanced stage or large tumors when screened biennially compared with those screened annually.

And, the cumulative 10-year risk for false-positive mammography fell from 58.5% to 37.5% in women not taking hormonal therapy, and from 65.8% to 43.2% among women who were taking hormonal therapy when biannual screening was compared with annual.

However, among women aged 40-49 years, those with extremely dense breasts had an 89% increased odds for advanced stage at diagnosis and a 139% increased odds for large tumor size when screened biannually compared with annual mammography. Yet the authors describe the benefits of annual screening in this group as "offset" by the increased risk for false-positive results and biopsy referral.

The American College of Radiology and the Society of Breast Imaging have strongly refuted the findings, saying that the authors used outdated endpoints, the study was nonrandomized, and did not account for the reasons why women might attend screening at different intervals.

In a joint statement they said: "[The] study authors would pose that a false-positive outcome is as bad as a true identification of cancer is good, when in fact the relevance of a false alarm pales in comparison to that of a potential life saved.

"Medical science cannot distinguish which cancers will never threaten the woman and which will become lethal. So the best medicine remains to find and treat the cancers found so they do not kill more women."

By Kirsty Oswald, medwireNews Reporter

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