Heather Bedard, C.H.E.
Many women who take oral contraceptives are unaware of how much their risk of some cancers increases. The cancers that contraceptives are more likely to produce are breast and cervical cancer due to the fact that these cancers have receptors for estrogen and progesterone. Contraceptives increase the levels of these hormones and in effect increase the risk of cancer. According to a prospective cohort study on contemporary hormonal contraception and the risk of breast cancer, the increased risk of breast cancer is low.[1] However, risk levels vary over multiple studies quite a lot. This is possibly due to selection bias or to the various types of contraceptives used. A case control study on breast cancer before 45 and oral contraceptive use, shows that women under the age of 45, who took oral contraceptives for less than 10 years, doubled their risk of cancer, and for those who took them over 10 years, their risk quadrupled.[2] In an analysis of 24 epidemiological studies of 16,573 women with cervical cancer and 35,509 women without cancer, the risks of cervical cancer increased as long as the consumption of contraceptives continued and declined after they were discontinued.[3] Better quality studies need to be done to more conclusively state the risk and reduction levels before and after use.
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[1] Mørch LS, Skovlund CW, Hannaford PC, Iversen L, Fielding S, Lidegaard Ø. Contemporary Hormonal Contraception and the Risk of Breast Cancer. N Engl J Med. 2017;377(23):2228-2239. doi:10.1056/NEJMoa1700732
[2] Miller DR, Rosenberg L, Kaufman DW, Stolley P, Warshauer ME, Shapiro S. Breast cancer before age 45 and oral contraceptive use: new findings. Am J Epidemiol. 1989;129(2):269-280. doi:10.1093/oxfordjournals.aje.a115132
[3] International Collaboration of Epidemiological Studies of Cervical Cancer, Appleby P, Beral V, et al. 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(9599):1609-1621. doi:10.1016/S0140-6736(07)61684-5