The second, the Canadian National Breast Screening Study, which began in the 1980s, also used annual mammograms and breast examinations for the screened group. But, in the control group, women aged 50-59 also received annual clinical breast examinations, and women aged 40-49 were given a single breast examination.
第二次是20世纪80年代开始的加拿大国家乳腺筛查研究，筛查组同样每年接受X光乳腺造影和乳房检查。但对照组50-59岁的女性同样每年接受临床乳房检查，而40-49的女性则接受一次性乳房检查。