The effectiveness of screening in the NHSBSP is influenced by pro- gramme factors, such as the introduction of two views and the opti- misation of optical density, and also by population factors, such as the increasing use of hormone replacement therapy during the 1990s. The current NHSBSP saves an estimated 1400 lives each year in Eng- land. The NHSBSP now diagnoses about half of all breast cancers found in women in the target age range of 50–70 years, with the remainder occurring in women who do not attend for screening or who present symptomatically in the interval between screens. Screened women are slightly more likely than.
