HPV and cancer
HPV, or human papillomavirus, is a virus that infects the skin and the cells lining body cavities. It is spread through close skin-to-skin contact. It is a very common infection which usually causes no symptoms at all.
Up to 8 out of 10 people will be infected with the virus at some point in their lives. HPV infections are usually on the fingers, hands, mouth and genitals. For most people, the infection will get better on its own and they will never know they had it. But in some people the infection will stay around for a long time and become persistent.
There are hundreds of different types of HPV. Most are harmless. But around 13 types of HPV can cause cancer. These are called ‘high-risk’ types. People with persistent infections with ‘high-risk’ HPV types are those who are most likely to go on to develop cancer.
How can HPV cause cancer?
Normally, HPV infections start in the deepest layers of the skin. During an infection, HPV causes skin cells to divide more than usual. New virus particles are then made inside these cells.
This fast skin growth can cause warts to develop, but often it doesn’t cause any symptoms at all. The types of HPV that cause warts are not the same types that cause cancer.
In some people with persistent ‘high-risk’ HPV infections, the virus damages the cells' DNA and causes cells to start dividing and growing out of control. This can lead to cancer.
Cervical cancer, screening and HPV
About 3,100 cases of cervical cancer are diagnosed in the UK each year. Nearly all are related to HPV.
HPV is spread to the cervix through sexual contact - not only penetrative sex. Using a condom reduces the chance of passing the infection on but it isn’t completely effective.
Most infections, even high-risk ones, are symptomless, so it is not always obvious if you or a partner carry HPV.
Taking up your cervical screening invitations is a great way of reducing the risk of cervical cancer. Screening aims to pick up early cell changes that are caused by HPV, and remove these cells before they have a chance to become cancerous.
By doing this, screening can prevent cervical cancer from developing in the first place. It prevents around 5000 deaths from cervical cancer a year in the UK, and many more cases of this cancer.
In England, the NHS are trialling using an HPV test as the main form of cervical screening, known as HPV primary screening. It doesn’t make any difference to what happens when you attend a cervical screening appointment. But your sample is examined in a different way in the lab –first of all it is tested for the HPV virus, and only if this test is positive will it be examined for cell changes that could be cancer. If the trials are successful, this type of testing will be rolled out across the country. HPV primary screening saves even more lives than the current test, so we hope that it will be rolled out as soon as possible.
HPV testing is already included in the cervical screening programme in England, Scotland and Northern Ireland for women who have borderline or mild changes in their first test. This is known as ‘HPV triage’ . If women are found to have a high-risk HPV infection, they will be referred for further examinations. If they don’t have an infection, they will continue to be screened normally. This should mean fewer women need to have further investigations or treatment when they wouldn’t have needed them.
Other HPV related cancers
HPV can cause cancers in other genital areas, like the vagina, vulva, penis and anus, as well as some types of cancer in the mouth and throat. As with cervical HPV infections, using a condom can reduce the risk of spreading HPV.
Vaginal, vulval, penile and anal cancers are less common than cervical cancer. Men who have sex with men may be at increased risk of anal cancer.
HPV infection also increases the risk of some types of mouth and throat cancers. Rates of mouth cancer, especially tongue and tonsil cancers, are on the increase, especially in people in their 40s, 50s and 60s. Estimates of how many of these cases are caused by HPV have varied, but it seems to be greater than 40% and the proportion of cases linked to HPV is rising. Mouth cancers linked to HPV have a better prognosis than cases which aren’t linked to the infection. There is still much more to learn about how HPV behaves in the mouth and how people can reduce the risk.
The main risk factors for HPV are the same for genital and oral infection. Having a high number of sexual partners increases your chance of picking up an infection.
Since 2008, girls aged 12-13 have been offered a vaccination against the two most common ‘high-risk’ types of HPV, HPV 16 and 18. Girls up to the age of 18 can request vaccination through the NHS if they weren’t vaccinated in year 8 (age 12-13).
This vaccine is very effective at preventing cervical cell changes and cancers associated with HPV 16 or 18 infection. Together, these two types cause about 7 out of 10 cervical cancers.
Since September 2012, the HPV vaccine used in the UK also protects against HPV 6 and 11, which are the HPV types that cause the majority of genital warts.
HPV vaccination has great potential to reduce the number of women who develop cervical cancer. But it is still important to take up screening invitations even if you have been vaccinated.
It is likely that the cervical screening programme will have to change when most women have been vaccinated against HPV 16 and 18. More research will be needed before it is clear what is the most effective way to screen women who have been vaccinated against HPV.
As HPV is linked to cancers in men as well as women, offering HPV vaccination to men would help reduce the risk of the disease. In particular, men who have sex with men have a higher risk of anal cancer than men who don’t. But it’s not completely clear yet whether this will be cost effective, so the Joint Committee on Vaccination and Immunisation, who advise the UK Departments of Health, are currently considering whether to offer HPV vaccination to teenage boys, and how men who have sex with men can be vaccinated practically and affordably.
Reducing the risk
HPV infections are mostly spread through direct skin-to-skin contact, usually during sexual activity. Practising safer sex by using a barrier method like a condom reduces the risk of passing on genital HPV infections.
The risk of HPV infection is higher for people who have had more sexual partners or who started having sex at an earlier age.
For cervical cancer, attending screening is a very important way of reducing the risk of developing the disease. And the HPV vaccination programme for girls offers them protection against the types of HPV responsible for about 7 in 10 cases of cervical cancer.