Cervical screening - who should have it and how often?

Cancer Research UK

All women aged between 25 and 49 should be offered cervical screening every three years, but five years is regular enough for women aged 50 to 64, according to a new report from Cancer Research UK.

Until now there’s been no precise direction on how often screening should be offered and it’s been left to individual Health Authorities to decide.

The researchers believe that their findings, published in the British Journal of Cancer1, offer explicit guidance on the best use of the NHS Screening Programme’s resources.

According to the most recent figures, 60 per cent of Health Authorities offer screening every three years, while the remaining 40 per cent opt for either five-yearly screening or a mixture of the two.

The new study is based on an audit of the NHS Cervical Screening Programme and compared screening histories of nearly 4000 British women, including 1300 who have been diagnosed with cervical cancer.

The researchers found that screening every three years offers 84 per cent protection against cervical cancer compared with 73 per cent with five yearly screening in younger women.

In older women, however, the audit shows very little difference between screening every five years and every three years. Even screening annually was little better than five yearly screening.

Screening works by picking up potentially cancerous changes, called cervical intraepithelial neoplasia (CIN), which can be removed to prevent cancer progression. Around 90 per cent of cases of CIN are diagnosed in women under the age of 45.

Lead author Professor Peter Sasieni, of Cancer Research UK’s Department of Epidemiology, Mathematics and Statistics at the Wolfson Institute in London, explains: “It would seem that cervical cancers in older women tend to develop much more slowly than tumours in younger women.

“In addition, cervical screening is much more effective in women over 50 and that’s why they need only attend for screening every 5 years.”

“A programme based on our recommendations offers over 80 per cent protection against cervical cancer for both age groups.”

Screening is routinely offered to women from age 20 and some doctors encourage younger women to be screened, if they are sexually active. However, the new study questions the value of screening women below the age of 25.

Cervical cancer is very rare in women under 25 and screening this age group picks up a great deal of false positives - women who appear to have early signs of cancer but in fact do not.

Experts believe that the benefits of picking up such a small number of cases are outweighed by the stress caused by so many false diagnoses.

“By offering screening in the most efficient way we believe we can prevent the great majority of cervical cancers in women who take part in the programme, while reducing the numbers needlessly referred to a gynaecologist for further investigations,” says Professor Sasieni.

Cancer Research UK’s Head of Clinical Programmes, Dr Richard Sullivan says: “The incidence of cervical cancer dropped by 42 per cent in the five years following the introduction of the screening programme.

“We know that every year cervical screening saves lives and we continue to urge women to attend for screening.

“This new research shows us how the programme can be refined and how resources can be maximised to benefit women.”

ENDS

  1. British Journal of Cancer88 (13)