Cervical Cancer Screening

The cervical cancer screening program in the UK is one of the most effective in the world. Women between the ages of 20 - 64 are invited to have a cervical smear test at three to five year intervals. The percentage of the eligible population being screened has risen from 45% in 1988-89 to 83.7% in 1999-2000. 

Although no screening program can be 100% effective, it is estimated that the screening program prevents between 1,100 and 3,900 cases of cervical cancer each year. The aim of cervical cancer screening is to detect abnormalities of the cervix at the pre-invasive stage of the disease. This is usually termed pre-cancer and implies an abnormality of the outer skin or epithelial layer of the cervix, which, if untreated may progress to invasive cancer. Cells shed from an area of pre-cancer may be detected by the cervical smear test.

Most (but probably not all) cancers of the cervix go through this pre-cancerous phase and its detection and treatment can effectively prevent the progression to invasive disease.It is believed that the majority of pre-cancerous changes are caused by infection with the human papilloma virus, or wart virus (HPV). Not all types of HPV cause pre-cancerous changes but certain strains of this virus are more prone to incorporate themselves into the nucleus of the cell and cause abnormal division of that cell which initiates the growth of the abnormal tissue. This process is called neoplasia (new growth).

The time scale from the initiation of the neoplastic process to the development of invasive cancer is usually over many years and therefore regular smear tests can detect this process before invasion occurs. When pre-cancerous cells are identified on a smear, the next step is an examination of the cervix to identify and, where appropriate, treat the abnormal area on the cervix. This examination is called colposcopy.