Research News

Pros and cons of drugs to prevent breast cancer

BMJ 2013; 346 doi: http://dx.doi.org/10.1136/bmj.f2891 (Published 08 May 2013) Cite this as: BMJ 2013;346:f2891

Pooled analyses of individual participant data from nine randomised trials have confirmed that selective oestrogen receptor (ER) modulators help prevent breast cancer in healthy women. Together, tamoxifen, raloxifene, arzoxifene, and lasofoxifene reduced the cumulative incidence of breast cancer by an estimated 38% relative to placebo in average or high risk women (4.2% v 6.3%; hazard ratio 0.62, 95% CI 0.56 to 0.69; number needed to treat 42). The protective effect was confined to cancers sensitive to oestrogen, and seemed to last for at least five years after the end of treatment. The drugs did not reduce mortality from breast cancer or other diseases, although they did reduce women’s risk of fractures, particularly vertebral fractures (0.66, 0.59 to 0.73).

All agents caused a significant excess of venous thromboembolic events. Tamoxifen in particular was associated with extra endometrial cancers (hazard ratio 2.18, 1.39 to 3.42). So, although these drugs work, they are not harmless, and the balance of risks and benefits will depend on a woman’s age, race, predicted risk of breast cancer, and whether or not she still has a uterus, says a linked comment (doi:10.1016/S0140-6736(13)60443-2). Predicting risk of breast cancer in well women is an inexact science, and women urgently need a convenient biomarker to help target preventive treatment at those with the most to gain and least to lose. Breast density is the most promising candidate so far, says the comment.

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Cite this as: BMJ 2013;346:f2891