In an effort to address the benefits and cast away the doubts about mammograms, a study of 210,000 Swedish women showed that mammograms reduced deaths from breast cancer by ~28% in women between the ages of 40 and 69. Another issue investigated was the benefit of screening women younger than age 50. The research indicated a similar reduction in deaths among those between 40 and 49 as in older women. Also, women who had mammograms during the 20 years after a screening program began in 1978 were 44% less likely to die from breast cancer, compared with women in the years before screening.The results of the study were published in the April 26, 2003, issue of The Lancet.
In making their determinations, the researchers took into account factors that could have biased results, including changes in breast cancer treatment and alterations in the incidence of breast cancer. They also accounted for possible errors in classifying women as having been exposed to screening, and the odds that their cause of death was wrongly classified.