Current users of oral contraceptives have almost doubled the risk of developing cervical cancer compared with never-users, but the risk declines after OCs are discontinued; researchers reporting in the Nov. 10 issue of The Lancet say the mechanisms are unclear.
Current users of oral contraceptives have almost doubled the risk of developing cervical cancer compared with never-users, but the risk declines after OCs are discontinued; researchers reporting in the Nov. 10 issue of The Lancet say the mechanisms are unclear.
Jane Green, MD, of the Cancer Epidemiology Unit at the University of Oxford in the United Kingdom, and colleagues pooled data from 24 studies of 16,573 women with cervical cancer and 35,509 without cervical cancer.
The researchers found that women on OCs who had used them for at least 5 years were significantly more likely to develop cervical cancer than never-users (RR, 1.9). But the risk declined after the drugs were stopped, reaching a level comparable to that of never-users after 10 years. The authors estimate that 10 years' on OCs starting at about age 20 increases the cumulative incidence of invasive cervical cancer by age 50 from 7.3 to 8.3 per 1,000 women in developing countries and from 3.8 to 4.5 per 1,000 women in developed countries.
"The increased risk overall in users of hormonal contraceptives is thus a valid measure of the effect of contraceptive use on the risk of developing cervical cancer, but tells us little about the possible mechanisms whereby use of hormonal contraceptives could affect the human papillomavirus-dependent pathway of carcinogenesis," the authors write.
International Collaboration of Epidemiological Studies of Cervical Cancer. Cervical 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. Lancet. 2007;370:1609-1621.