Prior Studies Underrated Benefit of Mammograms

The study was published in the May 1 issue of Cancer.

This is in contrast to studies done in the early 1970s, before the routine use of mammograms, which suggested that screening reduced the risk of death from breast cancer by only 30%. The new study involved almost 7,000 women in two counties, aged 20-69, diagnosed with breast cancer over a period of 29 years. Researchers compared the mortality rates of three periods that roughly coincided with no use, growing use, and full availability of mammograms. In the most recent period, the study showed that 85% of the women had regular mammograms. When the researchers included all women in the two counties, including women who did not have mammograms, they found that the risk of dying from breast cancer was 50% less than in the 1970s.

Since no significant increase in survival was found over time in either patients with breast cancer who were too young to have mammograms or among elderly women who refused to have them, the data suggest that almost all the benefit is due to the screening, say the researchers.