The research team revealed that inviting 100,000 women aged 20-24 for a smear test would prevent up to 23 cervical cancers overall. When they excluded very early stage cancers, where the treatment is often the same as for pre-cancers, routine screening prevented between three and nine invasive cancers from developing. But this would also mean an estimated 3,000 young women would be treated unnecessarily.
Screening picks up changes in the cervix which – in younger women – almost always return to normal without treatment. Screening under 25s means many would be treated unnecessarily for changes which would not have caused any harm if they had been left alone. And treatment brings side effects which, for a minority of women, include a risk of serious bleeding and increasing the chance of premature birth in later pregnancies.
The researchers estimated that to prevent one cancer from developing, the NHS would need to perform between 12,500 and 40,000 additional smear tests on women aged 20-24 and treat between 300 and 900 women in that age group.
Professor Peter Sasieni, Cancer Research UK’s cervical screening expert at Queen Mary University of London, said: “This research quantifies the risks and potential benefits of providing smear tests routinely in women under the age of 25. It seems clear that the risks outweigh the benefits. Decisions about screening programmes and who to invite should be based on careful analysis and it’s important to target screening at the right age group for the best possible outcome.
“Cervical screening is a very effective way of preventing cervical cancer in women over the age of 25. Our study shows that screening younger women leads to unnecessary treatment for many, resulting in serious side effects for some.
“This research makes it clear that the policy change to stop cervical screening in women aged 20-24 in England was well justified from a health perspective and was not a cost-cutting exercise.”
In England around 1,900 cases of cervical cancer are diagnosed each year in women aged 25-64. Since the cervical screening programme was introduced in 1988, cervical cancer incidence rates in England have dropped by more than 40 per centfrom 4,100 cases in 1988 to 2,300 in 2010.
Dr Julie Sharp, Cancer Research UK’s head of health information, said: “Whatever your age and whether or not you’ve had a smear test, it’s important to go to your GP if you notice anything out of the ordinary, like bleeding after the menopause, in between periods or after sex or pain during sex . It probably won’t be cancer but it’s a good idea to get checked out by your doctor who can arrange any necessary diagnostic tests.”
Dr Karen Kennedy, NCRI director, said: “This important research will help inform public health policy to provide the most effective programmes to save lives from cancer.”
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Notes to editors
*The team examined routine cervical screening data and cancer incidence statistics from England and Wales as well as unpublished data from the National Audit of Invasive Cervical Cancer.
** Inviting 100,000 women aged 20-24 for screening would result in around 119,000 extra smear tests, also called cervical screening tests, in total. Around 20,000 women would get abnormal results requiring follow up. This would result in an estimated 8,000 additional colposcopy referrals. A colposcopy is a procedure where the surface of the cervix is closely examined using a magnifying instrument called a colposcope.
*** In the UK around 2,400 cases of cervical cancer are diagnosed each year in women aged 25-64.
**** 42 per cent decrease in annual average age-standardised incidence rates, 1988-1990 compared with 2008-2010, females, all ages, England.
In England, Wales and Northern Ireland, women between the ages of 25 and 64 are invited to attend cervical screening. Between the ages of 25 and 49 women are screened every three years. Between 50 and 64 years women are screened every five years. In Scotland, currently women between 20 and 60 years women are invited for screening every three years.
But following recommendations from the UK National Screening Committee in 2012, Scotland will change its screening schedule in 2015 to match that of the other UK nations.