In 2003, approximately 211,300 new invasive cases of breast cancer (and 55,700 new ductal carcinoma in situ cases) and approximately 39,800 deaths due to the disease were estimated to have occurred in the United States. For a woman of average risk, lifetime breast cancer incidence is 7.8%, and mortality is 2.3%. Widely accepted techniques, for breast cancer screening, but with differing levels of evidence, include mammography, clinical breast examination (CBE), and breast self-examination (BSE), No cancer screening test has been studied more than mammography (with or without CBE).
Randomized Clinical Trials
Eight randomized trials have been conducted over more than 40 years to assess the impact of mammography. Together, these trials have included more than 5,00,00 women, with 180,000 women aged 40 to 49. The eight international RCTs have varied greatly. Most trials have included women in their 40s, although two trials began accrual at age 45. One of the Canadian trials (the first National Breast Cancer Screening study (NBSS1) was designed to examine mammography and CBE versus usual care for women in their 40s, with a separate study (NBSS2) to assess mammography plus CBE versus CBE alone women aged 50 to 59. The international studies have varied in key ways.
Randomized Clinical Trials
Eight randomized trials have been conducted over more than 40 years to assess the impact of mammography. Together, these trials have included more than 5,00,00 women, with 180,000 women aged 40 to 49. The eight international RCTs have varied greatly. Most trials have included women in their 40s, although two trials began accrual at age 45. One of the Canadian trials (the first National Breast Cancer Screening study (NBSS1) was designed to examine mammography and CBE versus usual care for women in their 40s, with a separate study (NBSS2) to assess mammography plus CBE versus CBE alone women aged 50 to 59. The international studies have varied in key ways.
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