[Screening for cancer. International knowledge and Danish practice].

Screening makes it possible to detect cancer before the disease gives rise to symptoms. A more effective treatment could thus be offered, and patients would then have a better prognosis. If screening works, mortality from a given cancer disease should decline in the screened population. At present three screening tests meet this requirement: 1) Pap smears for cervical dysplasia, with screening started at the latest at the age of 30 and not before the age of 20; 2) Mammography screening for breast cancer in women aged 50-69; and 3) faecal occult blood testing for colorectal cancer in men and women aged 50-74. But screening means the testing of healthy persons for cancer, and it therefore has a number of negative side effects, such as false positive and false negative tests. Whether or not screening is preferable in a given situation therefore depends on how the advantages are weighted against the disadvantages.