Cervical cancer – know the score on prevention
This week, 24th-30th January, is cervical cancer prevention week. Here we discuss what causes cervical cancer, how it can be prevented and how Worldwide Cancer Research has contributed to advances in cervical cancer.
How common is cervical cancer?
Worldwide, more than 527,000 women were diagnosed with cervical cancer in 2012, with incidence rates varying across the world. Unlike most cancers which affect older people, cervical cancer often affects women under 35.
What causes it?
The major cause of cervical cancer is the Human Papilloma Virus (HPV). Most people are infected with this virus at some point in their lives and for the majority of people it causes no serious ill effects and is cleared by the immune system quickly. However, in a small number of people HPV can remain ‘dormant’ (inactive) in their bodies for many years and can cause cervical cancer.
With funding from Worldwide Cancer Research, Dr Philippa O’Brien and Professor (Maria) Saveria Campo at the University of Glasgow were the first to show a possible reason for this prolonged infection back in the 2000s. MHC molecules are used by our cells to present parts of viruses or bacteria to immune system cells. This enables the immune system to recognise these foreign invaders and attack the infected cells to clear the infection. Dr O’Brien and Professor Campo found that a protein produced by HPV, called E5, reduces the number of MHC molecules that our cells produce.
With a separate grant, Professor Campo continued this work, and in 2010, proved that the E5 protein works by stopping cytotoxic T cells in the immune system from recognising the virus and trying to kill it. This allows the virus to manipulate the immune system and survive much longer. These important findings have added to the pool of knowledge that researchers are now using to find new treatments for people whose HPV infections have caused cervical cancer as well as cancers of the head and neck.
There are over 100 different types of HPV, some of which are responsible for genital warts, but these do not usually cause the cell changes that lead to cancer. Two strains in particular, HPV16 and HPV18 have been found to cause the majority of cervical cancer cases. However, there are several different subtypes of HPV16 and HPV18 found throughout the world. Back in the mid-2000s, scientists still didn’t know exactly how they varied and if they all caused cancer. With help from a Worldwide Cancer Research grant in 2008, Dr Gary Clifford and his team at the IARC in Lyon, France were able to study samples from thousands of HPV patients in 17 countries. He found that common HPV16 subtypes varied in different countries, and that these subtypes carried a varying risk of continuous infection and even cancer. His team was also able to identify new HPV subtypes not previously studied, many in Africa.
Dr Clifford’s work has helped to establish a unique ‘biobank’(a bank of biological data) of HPV variant data, and significantly contributed to understanding of HPV genetic variation and cervical cancer risk around the world.
Other risk factors
There are several other risk factors including smoking. If you smoke you are more likely to develop squamous cell cervical cancer than a non-smoker. We previously funded Dr Daniel Ndisang at University College London, who helped reveal one reason why women infected with the HPV virus are at a higher risk of the disease.
Are there ways to prevent it?
Yes, there is the HPV vaccination against strains HPV16 and HPV18 to prevent infection by these strains of the virus. There is also the cervical cancer screening test, known as the smear test designed to detect abnormal cells, before cancer even develops. In the UK there is also a recent recommendation for HPV testing before doing a smear test, as this could be more effective at informing women that they are at a higher risk of developing the disease. The HPV test is currently done only if abnormal cells are detected in a smear test.
The vaccine and smear test are not used everywhere in the world due to their cost and women are dying every day from this disease. More than 265,000 women are estimated to have died from cervical cancer around the world in 2012.
Screening saves lives
When diagnosed at its earliest stage, around 95% of women with cervical cancer will survive. But sadly, for advanced cervical cancer, the survival rates are way down at 5%. This is why the HPV vaccine and having a smear test is so vital. There are huge discrepancies between developed countries that have cervical cancer screening and the HPV vaccine and those that don’t. We have previously funded work trying to find new and cheaper ways to test for cervical cancer in developing countries but more work is needed until this is a reality.
Shockingly, recent figures released last weekend showed that 3.7 million UK women aren’t attending their cervical screening smear test. In fact a third of 25-29 year olds do not attend.
We urge anyone who is invited to attend cervical cancer screening or to have the HPV vaccine to do so as part of our mission to ensure no lives are cut short by cancer.