Women who take the contraceptive pill may increase their risk of cervical cancer, according to a major new study published in the Lancet1.
A team of scientists from Cancer Research UK and the International Agency for Research on Cancer conducted an extensive review of research on oral contraceptive use and cervical cancer risk – involving data from 24 countries.
Researchers found that the longer women used the pill the greater their risk of developing cervical cancer. The effect remained even when other risk factors for the disease such as infection with the Human Papilloma Virus (HPV) were taken into account.
Cancer Research UK experts stress that further research is needed to determine whether the risk of cervical cancer drops after women stop using the pill, before implications for public health can be fully understood. They also emphasise the importance of regular cervical screening for all women, whether or not they use the pill.
Persistent infection with some types of sexually transmitted HPV’s is thought to be the most important cause of cervical cancer. But whether women infected with HPV go on to develop cervical cancer may be affected by other factors such as the use of hormonal contraceptives. Some previous studies had suggested a link between cervical cancer and the pill but the evidence had been unclear.
In the study, commissioned by the World Health Organisation, researchers combined the data from 28 studies, involving 12,500 women with cervical cancer from a number of countries including the UK and USA.
They found that women who used the pill for five years or less had a 10 per cent increased risk of cervical cancer when compared with women who had never taken it. This increased risk rose to 60 per cent with five to nine years of use and doubled with 10 years of use or over.
A similar pattern of increased risk was seen when researchers took into account other factors which could influence cervical cancer risk, such as whether the women smoked, their number of sexual partners, whether they had previously attended cervical cancer screening and whether they used barrier methods of contraception.
Dr Amy Berrington from the Cancer Research UK Epidemiology Unit at the Radcliffe Infirmary in Oxford, says: “This study shows that use of hormonal contraceptives for long periods of time may increase the risk of cervical cancer.
“However, the public health implications of these findings largely depend on whether this risk remains long after use of hormonal contraceptives has stopped and this cannot be properly evaluated from published data. There is some evidence to suggest that the risk may drop after women stop using the pill but further research is needed to confirm this.”
She adds: “An international collaboration, funded by the World Health Organisation, has been set up to re-analyse original data to provide more reliable estimates of the risk of cervical cancer and pill use.”
Dr Lesley Walker, Director of Information at Cancer Research UK says: “Previous studies have shown that the pill may increase the risk of breast cancer and lower the risk of ovarian cancer. Now the new data suggests that it could raise the risk of cervical cancer. It’s vitally important that we continue to gather all the information we can on cancer risk and the pill so women can make fully informed choices about contraception.”
She adds: “We would continue to stress the importance of cervical screening whether or not women use the pill.”
- Lancet361 (5)
Around 3,200 women are diagnosed with cervical cancer each year in the UK.
The lifetime risk of being diagnosed with cervical cancer is 1 in 116 in the UK.
Cervical cancer is the second most common cancer in developing countries where the lifetime risk can be as high as 1 in 30.
The studies included in this analysis did not specify the dose or formula of contraceptives taken by the women. However, most women are likely to have taken the combined oestrogen and progestagen pill.