That's a much more significant impact than the 30% rate that has previously been attributed to mammography, says Smith, co-author of the long-range study that will publish its latest findings in the May 1, 2001 issue of Cancer. Even more deaths can be prevented if women get mammograms every year, as the ACS recommends for all women age 40 and older, Smith urges.

The Swedish study measured an organized program in which all the women in two counties between the ages of 40 and 69 received an invitation every two years to have a free mammogram. Between 1988 and 1996, among the women who actually got a mammogram, the breast cancer mortality rate declined by 63%.

"What I hope these data will do is, first, refute some recent studies that are inexplicably calling into question the very clearly demonstrated benefits of mammograms," Smith says. Those studies had weak methodology, Smith explains; such as, too-short study periods and not filtering out cancer deaths in women diagnosed before the mammograms were offered.

"Mammograms save lives by reducing the incidence rate of advanced breast cancer," Smith emphasizes. "We find breast cancer earlier. That way we can treat it earlier. By treating it early, before it has a chance to spread, we can save lives."

Smith says he hopes this new information will reinforce women who do get annual mammograms that they are doing the right thing, and, convince women who have been hesitant that they have a greater chance of benefitting.

"If policy-makers are going to invest in screening, they'll want to know what impact it will have," Smith says. "Another significant aspect of this Swedish study is that it provides data on mammography's impact in the community, rather than in a randomized, controlled clinical trial."

A number of studies in the past supported the conclusion that mammography had the potential to reduce breast cancer deaths by 30%; but, Smith explains, those studies did not filter out women who declined the mammograms, or women whose cancer was detected before they were offered screening.

In this new report from the Swedish study, the data are so detailed that Smith and his co-authors know which women were screened, when they were screened, and when their cancer was detected for the last 29 years. A rich legacy of reports has been published during those three decades, Smith says.

The study looked at an organized program of "invitation" to mammograms, in which women got regular reminders in the mail, and those who did not respond got subsequent notices that they were entitled to the free screening.

The US has no system to do such an invitational program, Smith explains, because the health care system is decentralized, and not really a system at all. But large HMOs have stepped up to the plate by starting such reminder programs.

One criterion that employers use in judging the quality of a health care plan is the percentage of women over the age of 50 in the plan who have had a mammogram, Smith says; so, HMOs and insurers have an incentive to alert women to the benefits of this screening.

All states but Utah require insurers and HMOs to cover the cost of a mammogram. Medicare and Medicaid also cover that cost.

Still, there are women who don't get them. If that was because 30% didn't impress them, Smith urges, maybe a 63% reduction rate will turn their heads.