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Contraceptive pill

In his editorial in the current New England Journal of Medicine David Hunter, Richard Doll Professor of Epidemiology and Medicine, reviews the evidence on the association between the use of oral contraceptives and risk of breast cancer.

A large prospective study by Mørch et al. in the current issue found a 20% higher risk of breast cancer among women, under the age of 50, in Denmark who were currently using or had recently used hormonal contraceptives than among those who had never used them. The results also showed that the risk increased with a longer duration of use. As most of the contraceptive formulations in the study have been widely used in Denmark since 1995, the results confirm that a risk that was initially reported with the use of older, often higher-dose formulations, also applies to current formulations of oral contraceptives. 

Mørch and colleagues analysed the risks associated with different formulations of oral contraceptives, particularly various progestins. The results did not suggest that any particular preparation is free of risk and the associations between the levonorgestrel-only oral formulation and the levonorgestrel-releasing intrauterine device (IUD) and breast cancer risk were unequivocally positive. 

Hunter notes that the higher risk of breast cancer among women who use or have recently used hormonal contraceptives must be placed in the context of the low incidence rates of breast cancer among younger women, and comments that the risk of breast cancer needs to be balanced against the benefits of using oral contraceptives: they provide an effective means of contraception, may help women with painful, heavy or prolonged periods, and their use is associated with substantial reductions in the risks of ovarian, endometrial, and colorectal cancers later in life. 

He concludes that these data suggest that the search for an oral contraceptive that does not elevate the risk of breast cancer needs to continue and that the current study exemplifies the opportunities to use population-wide “big data” approaches to evaluate important issues at a relatively low cost.