Clinical: Cervical cancer.

 
The essentials 
- High-risk strains of HPV appear in over 99 per cent of cervical 
cancers. 
- There is no proof that the Pill can cause cervical cancer. 
- Cervical cancer has few symptoms, so screening is very important. 
- Cells in the transformation zone are most vulnerable to being 
abnormal. 
- The best cervical smears are obtained using extended-tip spatulas. 

Cervical cancer affects approximately 3,200 women in the UK each year, and about 1,200 will die of the disease.

The NHS screening programme was set up in 1988. Since then, women between the ages of 20 and 64 years have been invited for cervical screening at least once every five years in England and Wales and every three years between the ages of 20 and 60 in Scotland. Smear rates have improved from about 50 per cent in the mid-1980s, to about 85 per cent in 1998.

Lower mortality rates

Between 1987 and 1997 the mortality rate dropped by about 40 per cent and since 1990 the incidence rate has also fallen, from 16 women per 100,000 in 1986 to 9.6 per 100,000 in 2000. A recent paper estimated that cervical screening has saved over 8,000 lives between the introduction of the computerised call-recall system and 1997. (Sasieni et al, 1999)

Cervical cancer is unusual in having a pre-invasive stage - cervical intraepithelial neoplasia (CIN) - which potentially makes it almost completely preventable by screening.

Types of cervical cancer

There are two types of cervical cancer, squamous cell carcinoma and adenocarcinoma.

Squamous cell carcinoma accounts for about 95 per cent of all cervical cancer, and this is the type to which we will be referring here. The major risk factors for squamous cell carcinoma appear to be related to sexual activity, and this is the rationale for advising screening only in women who are, or have ever been, sexually active. Virgins can develop adenocarcinoma, but the rarity of the disease makes the examination not worthwhile. Lesbians who have ever had a heterosexual relationship should be screened.

Risk factors

Infection with high-risk types of human papillomavirus (HPV or wart virus) is the most important risk factor. High-risk strains of HPV have now been demonstrated in more than 99 per cent of cervical cancers.

However, it is important to note that visible genital warts and HPV changes on a smear are not usually due …