Ovarian cancer and oral contraceptives

Abstract

Since the 1960s oral contraceptives have become a dominant form of female contraception in most developed countries. In the UK 25% of women aged 16-49 years and 62% of women aged 16-24 years rely on combined oestrogen-progestin or progestin-only (minipill) oral contraceptives. In the USA 19% of women aged 15-44 years (and 32% of 20-24-year-olds) take oral contraceptives. These drugs are the most effective reversible birth-control method and widespread use has been the cornerstone of family-planning initiatives worldwide. A causal role for oral contraceptives in various cancers was first suspected soon after their use became widespread but todays low-dose formulations are relatively safe drugs. Oral contraceptives have been linked with increased risks for some cancers (breast and cervix) and with protective effects for others (ovarian endometrial and colorectal). Calculation of the net effect on womens health is fraught with uncertainties. There are inherent difficulties associated with ascertaining the nature of exposure to oral contraceptives such as age at first use duration of use time since last use formulation of contraceptives (sequential combined or progestin-only) and dose. Furthermore epidemiological studies must include information about potential confounders such as sociodemographics family history of cancer comorbidity reproductive-health variables history of hormone-replacement therapy (HRT) and relevant lifestyle characteristics. For a woman in her 50s or 60s recalling past use of oral contraceptives is not easy. In case-control studies recall bias may further compound this problem because women with cancer might make a greater effort to recollect past exposures than their cancer-free counterparts. (excerpt)