Summary: Oral Contraceptives Increase Risk of Cervical Cancer

Study shows that among current users of oral contraceptives, the risk of invasive cervical cancer increases with increased duration of use. The risk seems to decline after the use of contraceptives stops.

• According to a recent study in the Lancet, the International Agency for Research on Cancer has classified oral contraceptives as a cause of cervical cancer. In order to research this claim further, 16,573 women with cervical cancer and 35,509 without cervical cancer were analyzed centrally. The women’s relative risks of cervical cancer were estimated by conditional logistic regression and arranged by study, age, number of sexual partners, age at first intercourse, status, smoking, and screening. Information from 24 studies worldwide was also pooled to investigate the association between cervical cancer and the pattern of oral contraceptive use. The researchers of the study found that among current users of oral contraceptives, the risk of invasive cervical cancer doubled with increasing duration of use (relative risk for 10 or more years’ of contraceptive use versus never used). The risk seemed to decline after the use of contraceptives stopped. A similar pattern of risk was found for both invasive and non-invasive cancer, and in women who tested positive for high-risk human papillomavirus. The relative risk of cervical cancer did not vary substantially between women with different characteristics. The researchers of this study concluded that the relative risk of cervical cancer is increased in current users of oral contraceptives and declines after the use stops. For every 1,000 women in more developed countries who use the pill between the ages of 20 and 30, the researchers estimated that less than one extra cancer (4.5 instead of 3.8 for never-users) can be expected by the age of 50. In less developed countries, the risk was estimated to be 8.3 cases per 1,000 decade-long oral contraceptive users, compared with 7.3 cases for every 1,000 never-users of oral contraceptives. These findings show the importance of regular cervical cancer screening for women who take oral contraceptives.¹

¹Cervical Cancer and Hormonal Contraceptives: Collaborative Reanalysis of Individual Data for 16,573 Women With Cervical Cancer and 35,509 Women Without Cervical Cancer From 24 Epidemiological Studies, The Lancet, Vol. 370, November 10, 2007, pp. 1609-1621.