STOCKHOLM, SWEDEN. Swedish researchers have reviewed the results of four mammography- screening trials carried out in Sweden up to and including 1996. The studies included 129,750 women who were invited to undergo screening (actual attendance rate was about 80 per cent) and 117,260 controls. The women were followed up for an average 15.8 years from time of entry to the study. During the follow-up there were a total of 22,398 deaths in the screening group of which 795 (3.5 per cent) were ascribed to breast cancer. The corresponding numbers for the control group was 20,945 total deaths of which 847 (4.0 per cent) were ascribed to breast cancer.
A closer examination of the data revealed that the benefits of mammography were limited to women between the ages of 55 and 69 years at the start of the study. The reduction in breast cancer mortality ascribed to mammography screening was 24 per cent (29 deaths per 100,000 women years versus 38 deaths per 100,000 women years in the control group) for the ages 55 to 59 years. It rose to 32 per cent for the age groups 60 to 64 years and 65 to 69 years. No statistically significant benefits were seen outside the age range of 55 to 69 years.
Dr. Karen Gelmon of the British Columbia Cancer Agency says that, "the data confirm that screening
mammography has a real but modest effect to decrease mortality from breast cancer and that effect varies
with age." She points out that it is still debatable whether mammography screening is of value for women
under 50 years of age.