See Carl Heneghan in action in the CEBM's workshop videos. 
Do you know the right age to start cervical cancer screening?
Last edited 17th September 2009
I guess the best blogs to write are the ones about subjects you don’t know the answer to. However, it always astounds me how many people can advise you on the answer about an important issue despite not knowing what the evidence actually says. So, when the recent British Medical Association conference voted on this issue (two thirds voted for the lowering of the age of screening to 20), my first thought was I would abstain, primarily due to lack of knowledge about the evidence-base on cervical cancer. I can see the headline now ‘98% of doctors refrain from voting as they have no knowledge of the current evidence’. Yet, the opposite always happens: no lack of opinion.
To address this important knowledge gap I need to understand what the current evidence is: you can try searching a different database than your normal comfort zone: try using PubMed or the National Library Health.
The first issue to be aware of is the UK government recently voted that 25 years of age should remain the age at which women start screening for cervical cancer in England. This followed the Jade Goody death which directly impacted on screening rates and moves to reduce the screening age.
From a Lancet article about the prevention of the cervical cancer epidemic in 2006 there were 56 cases in England in women under 25 (in 2009 this figure is estimated as 40); however, 1 in 3 women screened under the age of 25 would have an abnormal result (1 in 14 for over 25s). Mild abnormalities are common in the younger age group and would lead to many unnecessary investigations and subsequent treatments. This is not to say the change in mortality over the last 20 years has been nothing short of stunning; in 1988 the incidence in the UK was amongst the highest in the world as morality rates rose threefold between 1967 and 1988. Introduction of screening in 1988 has prevented an epidemic which has reduced by 2/3rds the number of deaths from cervical cancer which would have killed 1 in 65 of all UK women born since the 1950s if screening had not been implemented.
What I have learnt is that the question may be about the wrong age group to stop screening. More lives are lost to cervical cancer in women in their 70s than women under 30. Screening is most effective at saving lives if done about five years before loss of life peaked, in the UK this is aged 50 to 54.
Tags:
- Carl Heneghan's blog
- Login or register to post comments
The risks of cervical screening
"This is not to say the change in mortality over the last 20 years has been nothing short of stunning; in 1988 the incidence in the UK was amongst the highest in the world as morality rates rose threefold between 1967 and 1988. Introduction of screening in 1988 has prevented an epidemic which has reduced by 2/3rds the number of deaths from cervical cancer which would have killed 1 in 65 of all UK women born since the 1950s if screening had not been implemented."
Do you have any evidence for the "epidemic" theory?
I've seen one article over the years that was discredited.
I haven't seen any decent evidence to suggest that is the case beside someone's hunch.
Also, cervical cancer was in decline before screening started so clearly other factors were contributing to the decline. The number of women who've had hysterectomies would be one factor.
The numbers have fallen, but if you look at actual numbers they're quite small.
Dr Angela Raffles, UK cervical cancer screening expert, made the benefits of screening fairly clear - 1000 women need regular screening for 35 years to save ONE woman from cervical cancer.
(published in the BMJ)
Of course, 65% of women having 3 yearly screening will have a colposcopy and usually some sort of biopsy. Some of those women will be left with health problems.
Dr Richard DeMay, the American pathologist states that 99.35% of women derive no benefit from screening (including the 0.35% of women who get false negatives and may be disadvantaged by a later diagnosis) - so 0.65% of women derive a major benefit from screening.
Then we have an almost complete absence of informed consent and doctors being paid by the Governement to reach screening targets.
I'm afraid the more I look at this testing the more uncomfortable I become especially the miselading and incomplete information released to women and the lack of respect for a woman's right to choose.
I think many women are becoming very concerned about the ethics and value of this testing.
As a very low risk woman, I have always declined screening and faced the insults and bullying head-on at almost every visit to see a Dr. I'm able to stand up for myself, but it concerns me that many women are intimidated and scared into this screening.
I know many women who've endured the trauma of negative cone biopsies. I know these procedures are dismissed as "minor" by many doctors, but surely that should be a matter for every individual woman?
Is your risk profile such that you're happy to accept this risk of unnecessary biopsies or treatment? Instead most women are completely unaware of the risks and over-estimate the risk of this cancer. I think the hallmark of being a woman is now a damaged cervix.
I'm hopeful for greater honesty with breast and cervical screening and respect for informed consent.
CIN 3
It night be worth a look at the recent BMJ on this issues
Trish Groves did an excellent editorial
Editor's Choice
An embarrassment of riches
http://www.bmj.com/cgi/content/full/339/aug06_1/b3186
@
'Now a large population based study across the UK has provided compelling evidence to support the English stance (doi:10.1136/bmj.b2968). Peter Sasieni and colleagues found that although screening was associated with a 60% reduction of cancers in women aged 40, increasing to 80% at age 64, there was no evidence that screening women aged 22-24 reduced the incidence of cervical cancer over the next five years. While 73 women in this youngest group had cervical cancers, only five could be attributed to lack of screening'
Now Philip E Castle and colleagues have shown that, among women whose HPV infections don’t resolve within a year, the risk of developing high grade cervical intraepithelial neoplasia in the next three to five years is greatly increased (doi:10.1136/bmj.b2569). They propose repeated testing for the two most carcinogenic HPV types, 16 and 18, starting at age 25.
see the folliwng articles for more updatesand answers to your questions
http://www.bmj.com/cgi/content/abstract/339/jul28_2/b2546
Cytological surveillance compared with immediate referral for colposcopy in management of women with low grade cervical abnormalities: multicentre randomised controlled trial
TOMBOLA Group
BMJ 2009 339: b2546.
http://www.bmj.com/cgi/content/abstract/339/jul28_2/b2548
Biopsy and selective recall compared with immediate large loop excision in management of women with low grade abnormal cervical cytology referred for colposcopy: multicentre randomised controlled trial
TOMBOLA Group
BMJ 2009 339: b2548.
Options for managing low grade cervical abnormalities detected at screening: cost effectiveness study
TOMBOLA Group
BMJ 2009 339: b2549.
Cheers Carl
CIN & Immunosupression
I have recently had several women with 'Severe Dyskariosis' and histologically proven CIN3 . Q. is there proof of increased incidence in such women? In HIV positives I can understand but what about women with Chrone's Disease / Ulcerative colitis? what is the mechanism of their susceptibility?
harms with overdiagnosis
got a neat reply from evidence that matters on twitter
http://evidencematters.org/
@cebmblog 1 in 3 false +ves cervical screen <25yrs http://tr.im/sql4 Over-diagnosis occurs most at pre-invasive stage. http://tr.im/sqki
see sites for open access articles
http://www.thelancetstudent.com/2009/07/09/uk-cervical-screening/
http://breast-cancer-research.com/content/7/5/228
Cheers Carl
Age for cervical cancer screeing
Within Public Health clinics in WA we start cervical cancer screening 3 years after first intercourse or at age 20.
age to start screening
Intersting that you are starting after first intercourse, I've heard of this strategy before, therfore you must be screening in some individuals at age 16 or 17.
In terms of the evidence base were you aware of the high number of false positives in the under 25s, and maybe someone would like to comment on the adverse events associated with unwarranted investigations and treatment
Cheers Carl