Does Mammographic Detection of DCIS Prevent Invasive Breast Cancer?

With the advent of screening mammography, the number of diagnoses of ductal carcinoma in situ (DCIS) has grown substantially. Investigators in the U.K. assessed rates of DCIS diagnoses arising from screening mammograms from 2003 to 2007 in >5 million women (age range, 50–64) at 84 screening centers. They then compared frequency of DCIS diagnosis with incidence of interval invasive cancers (i.e., those found because of symptoms rather than through screening mammography) diagnosed within 3 years of the initial screen.

Mean frequency of screen-detected DCIS was 1.60 per 1000 women screened, and mean frequency of screen-detected invasive cancers was 5.53 women per 1000 screens. Subsequent interval cancers were diagnosed at a rate of 2.9 per 1000…