Cervical Screening and HPV

Author: Jenny Greenfield

Date: Mar 2015

Introduction

Every year in the UK over 3000 women will be diagnosed with cervical cancer. However, it is a largely preventable disease thanks to the cervical screening programme and HPV (Human Papilloma Virus) vaccination.1

Around five million women in the UK are invited annually for cervical screening. Cervical screening is a screening test to detect abnormalities at an early stage in the cells in the cervix and through this test, it is estimated that early detection and treatment can prevent up to 75% of cervical cancers from developing. Not going for cervical screening is one of the biggest risk factors for developing cervical cancer and it is within this group that almost half will develop cervical cancer.2

The NHS call and re-call system invites all women who are eligible for screening and registered with a GP. The system also keeps track of any follow-up investigation, and if all is well, re-calls women for screening-at either three or five years.

General concerns about cervical cancer prevention

Cervical screening attendance across the UK is in decline, particularly for the first and last ages to be invited (25-29 and 60-64). In recent years cervical screening in the 60-64 cohort has fallen dramatically to 72.7% in 2013, a drop of 5.3% from its peak in 2007 and is now at a 16 year low. When coupled with reports pointing to a rise in women having new relationships in later life, this may increase her risk of being exposed to HPV, which is the cause for over 99.7% of cervical cancers.1

In 2013 coverage amongst women aged 50-54 years (which is measured over a 5 year period) was highest at 81.6%.

For younger women aged 25-29 who may be due their first test, only 62% attended screening in 2013. However, this increased to 63.3% as from 31st march 2014, but it still means that less than 2 out of 3 women aged 25-29 years have been screened in the last three and a half years. The poor uptake is particularly worrying in this age group because cervical cancer is the most common cancer in women in the UK under 35, but only 7% of deaths occur in this age group.

The highest number of deaths occur in the 75-79 age group, but this is often because these women have not attended for screening.

A total of 4.24 million women aged 25-64 were invited for screening in 2013-14 and 3.23 million women were tested. (a fall of 2.9% from 2012-13 when 3.32 million were tested).1

Amongst women aged 25-64 with adequate tests in 2013-14, 93.4% had a negative result and 6.6% had a result categorised as abnormal (from borderline change through to potential cervical cancer). 1.3% of women tested in 2013-14 had a result showing high grade abnormality.1

Purpose of Screening

Any screening programme aims to detect abnormalities early so that treatment can be commenced with the aim of preventing any further disease progression. Cervical screening is very effective in detecting pre-cancerous changes and in the majority of abnormal screens, effective treatment can prevent progression to cervical cancer. Cervical cancer is now viewed as a preventable disease.3

HPV

There are over a 100 types of the HPV virus of which there are two high risk types, 16 and 18 which cause over 70% of cervical cancers. Of these 100 types, more than 40 will affect the genital area. Genital HPV is categorised as either:

  1. High-risk (oncogenic) types-that cause cervical intraepithelial neoplasia and invasive cancer. Particular high-risk strains include HPV 16, 18, 31, 33 and 45. These are associated not only with cervical cancer but also the vulva and vagina in women and also penile cancer in men and anal and oral cancers in both men and women.
  2. Low-risk types-that cause genital warts. HPV 6 and 11.

It is now universally accepted that HPV is a prerequisite for cervical cancer, 99.7% of cervical cancers are caused by HPV infection. The HPV is a small DNA virus, which infects the deeper layers of the skin and internal lining of organs such as the vagina and the mouth. HPV is often asymptomatic and normally resolves spontaneously-90% do so within 2 years. Persistent HPV infection causes the cell changes that eventually lead to cancer.

HPV infection is common and over half of all sexually active women will be infected by a strain of genital HPV at some point in their lifetime.

Women are most likely to be infected in their late teens and early twenties as these are usually the years when women are most sexually active.

HPV is spread by direct physical contact. i.e. genital contact, hand to genital contact. In fact anyone who is sexually active is a high risk. The risk of acquiring HPV also increase with the number of sexual partners.

HPV infection cannot be treated, but abnormal cell changes can be detected by screening and removed in colposcopy.4

HPV Vaccine

From 2012 Gardasil is the vaccine of choice, within the national vaccination programme. It is liscenced for girls over the age of 9 years and protects against 4 types of HPV. 16 and 18 which are high risk and 6 and 11 which are classed as low risk. Across the country this is a school based programme, where 13 year old girls are being vaccinated, but the DH are also looking at vaccination for boys.5

HPV testing

HPV testing was incorporated into the NHS Cervical Screening programme from April 2012. This means that screening can be more effectively targeted, which then reduces unnecessary procedures, i.e. attending colposcopy, and also the anxiety that is caused to women.

HPV triage is applied to women with borderline or low-grade cytology screening results, to help the labs determine whether women should be referred to colposcopy.

HPV testing was introduced so women with borderline changes or low-grade dyskaryosis are HPV tested to establish if they are high risk HPV positive. If HPV positive they are referred immediately to colposcopy. Women who do not have high risk HPV can be reassured and returned rapidly to routine recall.

The follow up of treated women in the NHS Cervical Screening programme has involved annual screening for up to 10 years before the return to routine recall. By employing the HPV test of cure approximately 80% of treated women will avoid having to undergo annual cytology tests.

Which samples are HPV tested?

Not all samples need to be HPV tested. HPV testing is conducted only on the first occurrence of a borderline or low-grade sample on eligible women routinely invited for screening. Testing for triage will also be done on all borderline and low-grade samples. Test of cure will be performed on all women who have been treated for CIN who have normal, borderline or low-grade cytology six months after treatment.4

What is HPV triage?

Only 15-20% of women with borderline nuclear changes or low-grade dyskaryosis have a significant abnormality that needs treatment. High-risk HPV testing in this group is effective in identifying which women may need treatment.

All cervical samples showing borderline nuclear changes or low-grade dyskaryosis are tested for high-risk HPV. Women who test positive for high-risk HPV are referred immediately to colposcopy and women who are high-risk HPV negative can be safely returned to routine recall.4

What is HPV test of cure?

This is where women who have a normal, borderline or low-grade cervical screening result six months after treatment for CIN and who also test negative for high-risk HPV, have a very low risk of residual disease. Samples taken six months post treatment that are cytology negative, borderline or low-grade are HPV tested.

Women whose samples are high-risk HPV negative proceed to three year recall-avoiding the need for 10 years of annual screening.4

Women who have a high-grade cytology result or are high-risk HPV positive six months after treatment are referred back to colposcopy.4

Refs

  1. NHSCSP. www.cancerscreening.nhs.uk/cervical/about-cervical-screening.html#whatis (accessed dec 2014)
  2. Jo’s Cervical cancer trust. www.jostrust.org.uk/Accessed Dec 2014.
  3. NHSCSP Publication No 23 "Taking sample for cervical screening - A resource pack for Trainers" (April 2006).
  4. Human Papilomavirus (HPV) and cervical cancer-The facts RCN 2012
  5. NHS Cancer Screening Series No 4 Consent to Cancer Screening

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Last revised: 3 March 2017

Next review: 3 March 2020