Some breast cancers mayregress spontaneously

Unexpected findings from a study of Norwegian women who have and have not received routine biennial screening mammography suggest some breast cancers may spontaneously regress.

Dr. Per-Henrik Zahl, a senior statistician at the Norwegian Institute of Public Health in Oslo, and colleagues compared cumulative breast cancer incidence in agematched cohorts of women before and after the initiation of biennial mammography.

The initiation of screening mammography has been associated with increased breast cancer incidence among women of screening age, the researchers said. If all the newly detected cancers progressed and became clinically evident as women age, a fall in incidence among older women should follow, but such was not the case in this study. Results were reported in the Nov. 24 issue of the Archives of Internal Medicine (2008;168[21]:2311-2316).