Women between the ages of 25 and 50 are offered smears at intervals of 3 years. Between 50 and 65 smears are offered at 5 yearly intervals. Smears are designed to find abnormal cells on the cervix (known as pre-cancer cells, dyskaryotic cells or CIN). By detecting pre-cancer cells and treating them if necessary, the development of cervical cancer in the future can be avoided. It usually takes many years for pre-cancer to develop into cancer. If pre-cancer cells are found on a smear, a recommendation may be made to perform a colposcopy. Often a test will be performed to check for the presence of high risk HPV (Human Papilloma Virus) at the same time as the smear is done. If there is high risk HPV present, then a referral will be made to colposcopy even if the smear shows only borderline or mild changes. This is because there is a slightly higher risk of finding high grade pre-cancer cells.
Colposcopy involves an outpatient visit. The doctor will examine the cervix with a speculum (the metal instrument used to open the vagina for smear tests). The cervix is examined with a microscope called a colposcope and if abnormal cells are seen, a biopsy (removal of a piece of tissue from the cervix) may be taken. This may cause mild discomfort.
A smear report may show one of a number of abnormalities
- Borderline changes – after 3 smears showing borderline change a recommendation to perform a colposcopy will be made. (If high risk HPV is present then a referral will be made after one borderline smear)
- Mild changes – after a smear with mild change a recommendation to perform a colposcopy will be made (unless a high risk HPV test is negative).
- Moderate change – colposcopy will be recommended.
- Severe change – colposcopy will be recommended.
Sometimes a smear will be reported as inadequate and require repeating. After 3 inadequate smears, a recommendation for colposcopy may be made.
Depending on the smear results and the findings at colposcopy, treatment may be recommended to remove the pre-cancer cells. Most commonly, treatment is in the form of a large biopsy performed under local anaesthetic in the colposcopy clinic. This is known as a Large Loop Excision of the Transformation Zone (LLETZ). Alternatively, if the abnormal cells are mild, it may be suggested to repeat the colposcopy after 6 months. This is because often, mild abnormalities can resolve without any treatment.
The cause of most cases of pre-cancer is the Human Papilloma Virus (HPV). Most people who are sexually active are exposed to HPV by sexual contact. For unknown reasons, some women seem more susceptible to the effects of HPV ie they develop pre-cancer. Stopping smoking reduces the chances of pre-cancer cells becoming more abnormal or developing into cancer. In the future HPV testing may be used to detect types of HPV likely to cause pre-cancer. This may be used to assess the need for treatment or observation. This approach is still being evaluated by the NHS.
The cervix cancer vaccine (Gardasil) has recently been licensed and it is likely that this will be offered to all teenage girls before they become sexually active. This will hopefully reduce the rates of pre-cancer in our population.