Effect of mammography screening on surgical treatment for breast cancer in Norway: comparative analysis of cancer registry data. A retrospective cohort study

All screening programmes tend to be somewhat controversial on the grounds of expense, logistics, and clinical value, but breast cancer screening is particularly so. The mammography programme for breast cancer screening, introduced to most Western countries during the 1980s and 1990s, has generated much debate over its efficacy. One difficulty is that the assessment of screening programmes cannot always incorporate trend changes in the incidence of breast cancer. Screening results are another concern—changes in the types of treatment offered, because of clinical advances, can make such results difficult to interpret. Furthermore, the outcomes that screening programmes choose to measure can vary; for example, whether mortality rates or mastectomy rates are the primary outcome. Not all suspicious lesions identified on mammography are premalignant or malignant, and even biopsied and confirmed cancerous lesions might regress spontaneously. These effects could lead to considerable overtreatment.1

Although several studies have investigated mortality from breast cancer