New mammography study shows no benefit to overall death risk

Bonnie: This study got very little exposure last week.

New research evaluating the timeline of mammography introduction and its effect on death from breast cancer in Sweden indicates no benefit of screening mammography on overall survival. The results appeared July 17th in the Journal of the National Cancer Institute.

Researchers evaluated data from the Swedish Board of Health and Welfare from 1960 to 2009 in women who were 40 years and older. They found that from 1972 to 2009, breast cancer mortality rates decreased by just under 1% per year, declining from 68.4 to 42.8 per 100,000 population, which is similar to the rate in the prescreening period.

In counties in which screening was introduced from 1974 to 1978, mortality trends during the next 18 years were similar to prescreening levels; in counties in which screening was introduced from 1986 to 1987, mortality increased by approximately 12% after the introduction of screening. In contrast, in counties in which screening was introduced in 1987/88 and in 1989/90, mortality declined by approximately 5% and 8%, respectively, after the introduction.

The lead researcher said that the "results reinforce the growing body of data showing that randomized trials on mammography screening were biased and ended up with results that suggest that reductions in breast cancer mortality are associated with screening." He added that mammography screening increases the diagnosis of indolent cancers that are not life-threatening (overdiagnosis).

Two editorials questioned the methods used in this study.