Study aims to counter Cochrane criticisms of mammography. (Skeptics Remain Unswayed).

The publication of a large Swedish study reporting a 21% reduction in breast cancer deaths in women who underwent screening mammography is the latest entry in the debate over the efficacy of such screening.

Although some experts are claiming that the study affirms the value of mammography, Danish researchers who have questioned its benefits aren't swayed by the data.

The mammography debate heated up last year after a controversial metaanalysis by the Danish Nordic Cochrane Centre reported serious flaws in many mammography studies (Lancet 358[9290]:1340-42, 2001).

To address those concerns, Lennarth Nystrom, Ph.D., of Umea (Sweden) University and associates reanalyzed four Swedish randomized controlled trials in light of the concerns raised about their validity by the Cochrane Centre.

The current analysis was based on the follow-up of 247,010 women in the four trials. In terms of all-cause mortality, mammography was associated with an age-adjusted relative risk of 0.98, which was not statistically significant. However, there was a significant 21% reduction in breast cancer mortality associated with mammography screening. The authors stressed that the advantageous effects of screening mammography on breast cancer deaths persisted for up to 18 years after randomization.

"We conclude that the recent criticism against the Swedish randomized controlled trials is misleading and scientifically unfounded," Dr. Nystrom and associates said (Lancet 359[9310]:909-19, 2002).

But Dr. Peter C. Gotzsche, one of the authors of the Cochrane critique, is not convinced. He said in an interview that he sees quality problems in the Swedish study. "It does not prove that screening prolongs life. Total mortality is not significantly reduced," he said.