"The lives of hundreds more cervical cancer patients could be saved if all those eligible went for screening," BBC News reports.
An analysis estimates an additional 347 deaths per year in England could be prevented if all eligible women attended cervical screening.
The NHS Cervical Screening Programme was set up to prevent deaths from cervical cancer, and women aged 25-64 are invited to attend regular appointments (depending on age, between every three to five years).
The analysis looked at screening history for more than 11,000 women in England diagnosed with cervical cancer, and matched controls without cancer. The study aimed to look at the potential impact of screening on diagnoses and deaths from cervical cancer.
It is estimated that the introduction of screening has reduced the number of cervical cancer in England by around two thirds.
However, if all eligible women attended screening regularly there could be even greater benefit - an additional extra 347 lives per year saved by screening. If cervical cancer is diagnosed at an early stage then the prospects of a complete cure are good.
It could well be the case that the issue of cervical cancer had dropped off the radar for many women since interest previously spiked after the death of reality star Jade Goody in 2009.
These results may suggest that more now needs to be done to encourage uptake by all eligible women.
Where did the story come from?
The study was carried out by researchers from the Centre for Cancer Prevention, Wolfson Institute of Preventive Medicine and was funded by Cancer Research UK. The authors declared no conflict of interest.
The UK media reported the story accurately. The Guardian included a statement from Nicola Smith, a senior health information officer at Cancer Research UK, pointing out that cervical screening wasn't just an issue for younger women. "Older women may not think this type of screening is relevant to them, but while cervical cancer is unusual in that it affects women at younger ages than most cancers, older women also develop the disease".
What kind of research was this?
This was a population-based case-control study. It compared screening attendance between women diagnosed with cervical cancer compared to controls without cancer.
This is the most suitable type of study for comparing the past behaviours and activities of people who have gone on to get the disease or not.
The study used data that had already been recorded before women did or did not get cervical cancer which removes the possibility of recall bias. However, this type of study still cannot prove that screening leads to prevention of cancer or death, as other confounding lifestyle factors may be involved in both a woman's likelihood of attending screening and her risk of cancer. But it is useful for looking at the possible impact of screening across a whole population, rather than just how it affects an individual.
What did the research involve?
Researchers used data from the Audit of Invasive Cervical Cancers (NHS Cervical Screening Programme, 2006), which was a population-based case-control study in England that is thought to include around 90% of all cervical cancers.
Cases were women aged 25-79 who had cervical cancer diagnosed in England between 2007 and 2013. Two age-matched comparison women were chosen for each, who did not have cervical cancer and had not had a hysterectomy.
Screening data was taken from routine records and included all NHS smears taken in the UK since 1988.
The odds of developing cancer for women regularly or irregularly screened were compared with women not screened in the past 15 years.
Cancer deaths within five years of cervical cancer diagnosis were analysed.
What were the basic results?
A total of 11,619 women were diagnosed with cervical cancer. More than a third of women were diagnosed between 35 and 49 years, and over a third were diagnosed with a small cancer still confined to the cervix (stage 1A).
Regular screening was associated with a 67% reduction in the odds of women (aged 35 to 64) being diagnosed with this early stage cancer, and a 95% reduced risk of being diagnosed with advanced stage 3 cancer that's spread into the pelvis.
In the absence of screening, it was estimated there would be more than double the number of cancers diagnosed in women aged 25 to 79 (relative risk [RR] 2.53, 95% confidence interval [CI] 2.39 to 2.68). If all eligible women were regularly screened, there would be around a third fewer cancers (RR 0.66, 95% CI 0.64 to 0.67).
Changing screening practices would have the greatest impact on women aged 50 to 64. Cancer rates would be about four times higher with no screening (RR 4.15, 95% CI 3.63 to 4.74). If everyone was regularly screened, rates in this age group would be less than half the current rate (RR 0.48, 95% CI 0.46 to 0.51).
In the absence of screening, cervical cancer deaths would be:
- four times higher for women aged 35 to 49 (RR 4.13, 95% CI 3.59 to 4.75)
- five times higher for women aged 50 to 64 years (RR 5.30, 95% CI 4.36 to 6.44)
If all women were regularly screened, mortality would be:
- less than half what it currently is for women aged 35 to 49 at diagnosis (RR 0.42, 95% CI 0.38 to 0.47)
- reduced by two-thirds for women aged 50 to 64 (RR 0.35, 95% CI 0.33 to 0.37)
How did the researchers interpret the results?
The researchers concluded they have shown "screening has an even larger impact on cervical cancer mortality than it has on [cancer diagnosis rates], and that if everyone attended screening regularly, 83% of cervical cancer deaths could be prevented, compared with 70% with current screening."
They also said that "these results are encouraging and should be used to promote, among women, regular attendance to screening and, among policy makers, the implementation of organised screening programmes in areas not yet covered."
They conclude "a further 347 deaths per year could be prevented if everyone attended screening regularly between ages 25 and 64 years".
More than 11,000 records were analysed in this study investigating the association between cervical cancer screening and cervical cancer rates and related deaths. The strength of this study is the vast number of women included and the use of screening data going back up to 15 years.
The findings suggest that screening currently prevents thousands of cervical cancers each year. However, if uptake were improved further and all eligible women attended regular screening, even more cancers could be avoided and lives saved.
One note of caution though is that the study still can't prove that cervical cancer screening is wholly responsible for any differences in cancer diagnoses or mortality rates between cases and controls. There may be important lifestyle factors that are associated both with risk of cervical cancer and likelihood of attending screening.
Women who smoke are at increased risk of cervical cancer, as are women who have unprotected sex with multiple partners (increasing their risk of acquiring the HPV virus that causes the cancer). It is possible that some women with these risk factors could also be less likely to follow other healthy lifestyle practices, such as attending regular screening.
Nevertheless, the study suggests that uptake of the cervical cancer screening programme could be improved. To do this, health practitioners and policy makers could further promote uptake among women aged 25 to 64.
If you are unsure if or when you should attend a cervical screening appointment then contact your GP for advice.
"The lives of hundreds more cervical cancer patients could be saved if all those eligible went for screening," BBC News reports. An analysis estimates an additional 347 deaths per year in England could be prevented if all eligible women.
Links to Headlines
Cervical screening 'could save hundreds more lives'. BBC News, September 16 2016
Full uptake of cervical cancer screening could save hundreds of lives. The Guardian, September 16 2016
Why you should NEVER miss a smear test: Cervical screening 'saves 2,000 lives a year'. Mail Online, September 16 2016
Links to Science
Landy R. Pesola F, Castañón A, Sasieni P. Impact of cervical screening on cervical cancer mortality: estimation using stage-specific results from a nested case-control study. British Journal of Cancer. Published online September 15 2016
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