Women over 50 are being urged to have regular smear tests after research showed that those who do not attend screenings are six times more likely to develop cervical cancer than those whose tests have been normal.
A study from Cancer Research UK scientists found women who fail to have smear tests over 50 have a much higher chance of developing the disease compared with other women the same age who have a history of normal screening results.
Researchers also found that women with a screening history and normal screening results between the ages of 50 and 64 have a lower risk of cervical cancer at least into their 80s. Researchers examined data taken from 1,341 women aged 65 to 83 who were diagnosed with cervical cancer between 2007 and 2012, and compared them to 2,646 women without the disease.
Among those women who skipped smear tests between the ages of 50 and 64, 49 cases of cervical cancer were diagnosed per 10,000 women at the ages of 65 to 83.
This compared with just eight cases per 10,000 women among those with an adequate screening history and normal results. Women who had been screened regularly but had an abnormal result between the ages of 50 and 64 had the highest risk of all – 86 cervical cancer cases per 10,000 women at age 65 to 83.
In England and Northern Ireland women aged 25 to 49 are offered screening every three years, and every five years between 50 and 64.
Professor Julietta Patnick, director of the NHS Cancer Screening Programmes, said women could control their risk of cervical cancer through regular screening.
"Any abnormalities that might be found can then be treated in order that they do not go on to develop into cancer. Where a cervical cancer is found through screening, it is usually at a very early stage where treatment has a greater chance of success," Patnick said. "It is essential that women are aware of this when deciding whether or not to be screened."
Meanwhile, women who have been found to carry abnormal cells in their cervix are at much greater risk of later developing and dying from cervical or vaginal cancer, a Swedish study shows. The study of 150,883 women who had been treated for CIN3, cells that can be a precursor to cancer, found that they were the most at risk from cancer when their reached their 60s or 70s.
A paper on the British Medical Journal's website reports: "Women previously treated for CIN3 are at increased risk of developing and dying from cervical or vaginal cancer, compared with the general female population.
"Women previously diagnosed with, and treated for, CIN3 were at substantially increased risk of developing cervical or vaginal cancer when they reached 60. The risk accelerated with further ageing."Among Swedish women the lifetime or background risk of developing either cancer is 8.9 cases per 100,000 women, and 10.2 cases per 100,000 in women who are aged at least 70. But among the women in the study who had CIN3 the rate was more than 70 per 100,000 women aged 70 – seven times that of the general population of that age.
The authors stress that while cervical cancer screening helps prevent many cases of, and deaths from, the disease, those treated for CIN3 nonetheless face "a steep increase in risk of death with increased age after previous diagnosis of CIN3". The risk more than doubled 30 years after the treatment, they said.
In the UK about 2,851 women were diagnosed with cervical cancer in 2010, making it the 12th most common female cancer, while 972 women died from it during 2011. Although all women aged 25 to 64 are offered screening, just under four in five take up the offer, and attendances have been falling since 2003, according to Public Health England. While 4.24 million were invited to screening in 2012-13, just 3.32 million (78.3%) made the appointment. The biggest fall in attendance has been with women aged 25 to 49.
In those 3.32m tests 6.5% gave abnormal results and 0.6% of the women had CIN3. The NHS cancer screening programme could not say how many women a year are treated for CIN3. Women treated for CIN3 have a colposcopy plus one of five procedures, such as a cone biopsy, cryotherapy or laser treatment. Sarah Williams, Cancer Research UK's health information officer, said cervical screening saved thousands of lives. "This study highlights how important it is to keep an eye on women who've had abnormal cells in their cervix. In the UK, these women have follow-up screening tests and tests for the HPV infections that cause cervical cancer, to reduce the risk of the abnormal cells coming back."
Robert Music, chief executive of Jo's Cervical Cancer Trust, said the study highlighted a need to look at the follow-up treatment of women with CIN3. omen over 50 are being urged to have regular smear tests after separate new research studies by Cancer Research UK indicated that those who do did not attend are were six times more likely to develop cervical cancer than those whose test results were normal.
In England and Northern Ireland women aged 25 to 49 are offered screening every three years, and every five years between 50 and 64.
Professor Julietta Patnick, director of the NHS Cancer Screening Programmes, said women could control their risk of cervical cancer through regular screening.
"Any abnormalities that might be found can then be treated in order that they do not go on to develop into cancer. Where a cervical cancer is found through screening it is usually at a very early stage where treatment has a greater chance of success. It is essential that women are aware of this when deciding whether or not to be screened."
• This article was amended on 15 January 2014. An earlier version referred to a colonoscopy when colposcopy was meant. This has been corrected.