Researchers in Sweden, the United Kingdom, Taiwan, and the United States report in the current edition of The Lancet that mammograms do reduce the risk of breast cancer among women, finding that women who get regular mammograms reduce their risk of dying from the disease by 28%. The study was the largest and most rigorous yet to investigate the survival benefits of routine breast mammograms, involving analysis of the health records of more than 210,000 Swedish women ages 20 to 69 over a 40-year period. "While mammography is largely accepted by the scientific and medical community as a benefit to women, there are still some who express doubts as to its value," said lead study author Stephen Duffy. "This study goes a long way toward silencing the dissenting voices."
Mammograms can detect small tumors up to two years earlier than breast exams, providing more options for treatment. Recommendations that women have regular mammograms have been based on seven experiments conducted in the 1970s and 1980s that concluded the X-rays can cut deaths from breast cancer significantly. However, confidence in breast screening was shaken by Danish scientists in 2000 who reanalyzed the experiments and concluded that five were so flawed, it was impossible to tell if routine mammograms saved lives. Several expert panels also questioned the benefits of regular mammograms.
In the latest study, researchers compared deaths from breast cancer diagnosed in the 20 years before mammogram screening was introduced with those diagnosed in the 20 years afterward. The X rays were introduced in 1977 and offered to all women over 40. The study found that among women who got regular mammograms, the risk of dying from breast cancer was reduced by 44% compared with the breast cancer death rate before mammograms became available. Women who refused mammograms after they became available still saw a 16% reduction in the chance of dying from disease due to factors other than mammography, such as better cancer treatments.