NEW YORK (Reuters Health) - In the wake of recent controversy over the value of regular breast cancer screening with mammography, a new analysis shows that mammograms can make a modest difference in a woman's risk of dying from the disease--at least if she's 55 or older.

The debate over whether mammograms actually save women's lives arose from two Danish researchers' re-analysis of data from the several studies that helped form the basis of current screening guidelines. They concluded that these trials--from Sweden, the US, UK and Canada--provided no reliable evidence that early detection with mammography cuts breast cancer mortality.

This latest analysis looked at the four Swedish trials, this time with longer-term data. Based on a follow-up of up to 20 years across the studies, mammography was associated with a 21% reduction in breast cancer deaths overall, according to findings published in the March 16th issue of The Lancet.

"The benefit of screening was maintained several years after the trials had been closed," report Dr. Lennarth Nystrom, of Umea University in Sweden, and his colleagues.

Further, they add, "the recent criticism against the Swedish...trials is misleading and scientifically unfounded."

The researchers came to this conclusion after looking at some of the concerns raised about the design of the studies--such as perceived flaws in the ways women were randomly assigned to have or not have mammography. They argue that these trial-design issues would not appreciably affect the study outcomes.

Nystrom's team did find that the benefits of mammography differed by age, with the greatest benefit seen among women in their 60s. Overall, the benefits in terms of lower risk of dying from breast cancer were significant starting at age 55. There was a "small effect" among women in their early 50s, the researchers note.

In the US, current guidelines call for women to begin getting mammograms every year or two at age 40. And although these younger women may benefit, debate continues about the "size" of the effects, according to an editorial accompanying the report.

"So where does this...leave clinicians and women?" write Drs. Karen A. Gelmon and Ivo Olivotto of Canada's British Columbia Cancer Agency.

The editorialists conclude that the new analysis confirms that mammography has a "real but modest effect to decrease mortality from breast cancer and that this effect varies with age."

They also argue that the true benefits in terms of lives saved "can only be measured many years and even decades after the start of screening."

According to Gelmon and Olivotto, "Women who are otherwise well, especially those aged 55 to 69 years, and who are concerned about breast cancer should be encouraged to attend screening."

It's time, they assert, for the "angst" about breast cancer to move on from the debate over mammography and focus on questions of how to prevent and better treat the disease.

SOURCE: The Lancet 2002;359:904-905, 909-919.

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