An article in this weeks
Archives of Internal Medicine from the Norwegian Screening Programme, discuss how there is an excess of cancers in the screened population, and how some of these regress spontaneously
Arch Intern Med. 2008;168(21):2311-2316
it appears that some breast cancers detected by repeated mammographic screening would not persist to be detectable by a single mammogram at the end of 6 years. This raises the possibility that the natural course of some screen-detected invasive breast cancers is to spontaneously regress