Screening for cancer and pre-cancer.

In some countries cervical screening has been established for many years and has had a considerable impact on mortality from invasive cervical cancer. Because of this success, and in view of the continued high incidence and mortality from cancers generally, there is much interest in extending screening for other types of cancer. One example is the more recent introduction of mammographic breast screening in the UK. For other cancers, such as those of the colon, rectum, prostate and ovary, screening is currently confined to demonstration projects. Much of the success of cervical screening is attributable to the fact that abnormalities are detectable at a pre-cancerous stage, and treatment is effective in halting progression to invasive cancer. This is not always the case for most other forms of cancer screening.