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, often during sexual activity. 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 body will clear the infection 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 12 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, including genital 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.
HPV, cervical cancer and screening
About 3,100 cases of cervical cancer are diagnosed in the UK each year. Nearly all are related to HPV. But it’s important to remember that most women with HPV don’t develop cervical cancer.
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 at least 2000 cervical cancer deaths each year in the UK, and many more cases of this cancer.
In England, the NHS has been 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 if this test shows HPV in the sample, it will be examined for cell changes that could be cancer. In 2016 the National Screening Committee recommended that this type of testing should 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. England and Wales have committed to this, but there are currently no plans to offer HPV primary screening in Northern Ireland and Scotland. .
HPV testing is already being used in the cervical screening programme in England, Wales 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 invited for more tests. If they don’t have an infection, they will continue to be screened normally. This should mean fewer women need to have further tests or treatment when they wouldn’t have needed them.
What other cancers are linked to HPV?
HPV can cause cancers in other genital areas, like the vagina, vulva, penis, and anus, as well as some types of cancer of the mouth and throat. As with cervical HPV infections, using a condom can reduce the risk of spreading HPV. Other factors can increase the risk of HPV-related cancers. For example, women who smoke have a higher risk of cervical cancer than those who don’t smoke. It’s thought women who smoke are more likely to have HPV infection and are less able to clear the infection.
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, particularly in people in their 40s, 50s and 60s. Estimates of how many of these cases are caused by HPV have varied from around 20% to more than 50%, and the evidence suggests that 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 11-13 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 at age 11-13.
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.
The HPV vaccine now used in the UK (Gardasil) also protects against HPV 6 and 11, which are the HPV types that cause the majority of genital warts.
Gardasil has been rigorously tested in large studies and has been shown to be safe. Any side effects are usually mild and include things like pain around the injection site or headaches, There have been a small number of reports claiming the HPV vaccine is linked to conditions called chronic regional pain syndrome (CRPS) and postural tachycardia syndrome (PoTS). In 2015 the European Medicines Agency looked at all the evidence and did not find a link between the HPV vaccine and these conditions.
HPV vaccination has great potential to reduce the number of women who develop cervical cancer. But screening is still important, even if you have been vaccinated, as the vaccine doesn’t protect against all types of HPV.
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 is needed to tell us how best 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 disease. In particular, men who have sex with men have a higher risk of anal cancer than men who don’t. In late 2015, the Joint Committee on Vaccination and Immunisation, who advise the UK Departments of Health, recommended that the HPV vaccine should be offered to men who have sex with men who attend sexual health (GUM) and HIV clinics. In England, a pilot study is now underway in selected clinics to see how this programme could best be delivered, while Scotland, Wales and Northern Ireland have committed to offering the vaccine in all sexual health and HIV clinics.
The Committee are also currently considering whether to offer HPV vaccination to all teenage boys.
Reducing the risk
HPV infections are mostly spread through direct skin-to-skin contact, usually during sexual activity including oral sex. The risk of HPV infection is higher for people who have had more sexual partners or who started having sex at an earlier age. HPV can be spread between opposite-sex or same-sex partners.
But it’s important to understand that while the virus can spread through skin-to-skin contact, you cannot directly pass on HPV-linked cancers.
Practising safer sex by using a barrier method like a condom reduces the risk of passing on genital HPV infections, but it isn’t completely effective.
A person can have HPV for a number of years without knowing, especially because in most cases there are no symptoms. If someone is found to have the infection, it’s not possible to draw any conclusions about how or when they became infected with HPV, or how long they’ve had it for. There is currently no reliable way to test for HPV in men.
For cervical cancer, attending screening is a very effective 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.