Previous studies have suggested that women under the age of 50 should receive mammographic screening more frequently than every two to three years to reduce their mortality rate from breast cancer. Bjurstam and associates evaluated the impact of mammography every 18 months on breast cancer mortality among women aged 39 to 49 years as part of the Gothenburg Breast Screening Trial.

Between September 1983 and April 1984, a total of 11,724 women aged 39 to 49 years were invited to begin receiving mammographic screening every 18 months. Two-view mammograms were performed unless earlier examinations indicated that a single view was adequate for screening. These women were matched with 14,217 women who did not undergo mammographic screening until the sixth or seventh year of the study.

During the study period, breast cancer was diagnosed in 144 women in the mammographic screening group and in 195 women in the control group. Eighteen women in the screening group died of breast cancer compared with 40 women in the control group, representing a 45 percent reduction in mortality from breast cancer. In women who were compliant with the recommended 18-month interval, the reduction in mortality increased to 49 percent.

The authors conclude that an 18-month screening interval for mammography in women aged 39 to 49 years has a significant impact on reducing breast cancer mortality. Organizations that develop mammographic screening recommendations should consider these new findings when formulating mammography guidelines for women under 50 years of age.