ARTICLES Canadian National Breast Screening Study-2: 13-Year Results of a Randomized Trial in Women Aged 50–59 Years

Background: Screening for breast cancer with mammogra-phy in women aged 50 years or more has been shown to reduce mortality from breast cancer. However, the extent to which mammography contributes to the reduction of mor-tality in women who also undergo physical examination of the breasts is not known. This study was designed to com-pare breast cancer mortality following annual screening con-sisting of two-view mammography and physical examination of the breasts with mortality following annual screening by physical examination only. Breast self-examination was taught to all participants. Methods: This trial randomly and individually assigned 39 405 women aged 50–59 years, re-cruited from January 1980 through March 1985, to one of the study arms. The women were followed by record linkage with the Canadian National Cancer Registry and Nationa