Digoxin and breast cancer.

Several epidemiological studies, some of which included several thousand women, have shown a link between digoxin exposure and the risk of breast cancer. A cohort study of women with angina, identified in the Danish Prescription Registry, showed a statistically significant increase in the risk of breast cancer among women taking digoxin compared with those not taking digoxin. An increase in the risk of breast cancer of similar magnitude was observed in a case-control study based on Danish hospital registries. In both studies, the risk of breast cancer was increased by about one-third with digoxin (relative risk around 1.3). A causal link is plausible, given the oestrogen-like properties of digoxin. In practice, this risk must be taken into account, especially in patients at risk of breast cancer. Women should be informed of the increased risk of breast cancer before deciding whether the impact of digoxin on cardiac symptoms warrants taking this risk.