An article published on March 7 in PLoS Medicine revealed that women who use injectable contraceptives increased their risk of developing certain female cancers. The cancer risks associated with the use of oral contraceptives were known prior to this study; the cancer risks of injectable contraceptive use were unknown.
The study, which was conducted and published by Dr. Margaret Urban and her global peers, analyzed epidemiological case-control data obtained from a South African hospital. Data compared self-reported contraceptive use (oral and injectable) in black South African females diagnosed with breast, cervical, ovarian, and endometrial cancer to self-reported contraceptive use in a control group of women who had cancers that had no known relationship to hormonal contraceptive use.
The researchers found that women who were either current or previous users of hormonal contraceptives had significantly increased incidence of breast cancer over women who had never used them; incidence was significantly increased regardless of the form of contraceptive used (injectable or oral). Incidence of cervical cancer was also significantly increased in users of injectable contraceptives but not oral contraceptives. However, the researchers found that the incidence of breast cancer and cervical cancer were not significantly increased in women who ceased their use of hormonal contraceptives in the ten years or more prior to the study.
Women who had used injectable contraceptives, exclusively, for five or more years prior to the study had significantly higher incidence of ovarian cancer than women who had never used them. Finally, women who had used oral and/or injectable contraceptives, but not exclusively injectables, had a significantly higher incidence of endometrial cancer. The researchers concluded that incidence of female cancers were similar regardless of how the contraceptive was administered.