A study by researchers at the University of Toronto has shed more doubt on the effectiveness of mammograms in helping in the fight against breast cancer, with their research showing that women who undergo mammograms before age 50 do not have a reduced risk of dying from the disease. The Canadian study involved 50,430 women in their 40s recruited from 1980 to 1985 to participate in the Canadian National Breast Cancer Study. Half of the participants had annual mammograms, while the other half underwent only annual physical examinations. By 1996, 592 women in the mammogram group had been diagnosed with invasive breast cancer, and 105 had died. Among women who did not receive mammograms, 552 were diagnosed with cancer, and 108 died.
"The data from this research is quite striking and quite clear," said Cornelia Baines, coauthor of the study. "The difference between annual screening compared with the control group is not statistically significant. Breast cancer mortality was not reduced."