In our article on oral contraceptives (OCs) we state that ‘oral contraceptives increase the risk of breast cancer with long-term use but reduce the risk of endometrial and ovarian cancer’. Some commentators have questioned the breast cancer risk. The UK National Case-Control (UKNCC) study, which looked at oral contraceptive use in women with breast cancer diagnosed before age 36, found a trend for increased risk associated with duration of use.1 ‘The simplest and most plausible explanation’, say the authors of the study, ‘must be that there is a substantial causal relation between prolonged use and breast cancer in young women.’ The increased risk seems to be associated particularly with OC use before the first full-term pregnancy.2 Several studies found no excess risk in OC users aged 45 or over, few of whom had taken the pill before their first pregnancy.3–5 In the UKNCC study the relative risk of breast cancer was 1.43 after 4–8 years’ use and 1.74 after more than 8 years’ use. In broad terms this means that three women in 1000 who use oral contraceptives for 4 or more years might be expected to be under treatment for breast cancer by age 36, compared with two per 1000 non-users.
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