Current users of oral contraceptives are at increased risk of developing cervical cancer, however 10 years after stopping use the risk returns to that seen for never-users.
Jane Green, Cancer Epidemiology Unit, University of Oxford, UK and colleagues from the International Collaboration of Epidemiological Studies of Cervical Cancer pooled and re-analysed data from 24 studies worldwide, which included over 16000 women with cervical cancer and over 35000 without.
The study confirmed previous evidence that among current users of oral contraceptives, the risk of invasive cervical cancer increases with increasing duration of use -- with those who have used contraceptives for five years or more having about twice the risk compared with never users.
This study showed for the first time how long this effect persists after oral contraceptive use stops.
A similar pattern of risk was seen both for invasive and in-situ cancer, and in women who tested positive for the high-risk type of human papillomavirus which causes cervical cancer.
The authors estimated that 10 years use of oral contraceptives from around age 20 to 30 years increases the cumulative incidence of invasive cervical cancer by age 50 from 3.8 to 4.5 per 1000 women in more developed countries, and from 7.3 to 8.3 per 1000 women in less developed countries.
In the long term the extra risk of cervical cancer in oral contraceptive users is more than outweighed by a reduction in risk of ovarian and endometrial cancers.
Source: The Lancet, 2007