Hydralazine and breast cancer

Hydralazine (CAS: 86-54-4; 1-hydrazinonaphthalazine) is a well-established antihypertensive agent. There are no conclusive data on the drug as a human carcinogen, but one of its metabolites, hydrazine (CAS: 302-01-2), has been shown to be carcinogenic in rats and mice. To assess the relationship of hydralazine to human breast cancer, 3,419 women with breast cancer and 3,219 hospital control subjects were studied. Data were obtained by interview in hospitals in the United States and Canada. A total of 1.4% of the cases and 1.2% of the controls had used hydralazine. Compared with never use, the relative risk (RR) estimate for hydralazine that was first used at least 18 months before admission was 0.9 [95% confidence interval (CI), 0.5-1.7] after risk factors for breast cancer and the use of other antihypertensive drugs and diuretics were taken into account by multivariate analysis. The RR estimate for hydralazine use lasting at least 1 year was 0.9 (95% CI, 0.5-1.7). RR estimates for longer durations of use (up to 5 or more yr), and for use within strata of risk factors for breast cancer, were close to 1.0. The results suggest that hydralazine does not increase the risk of breast cancer in humans in the short term. Whether the risk is increased after latent intervals of many years could not be evaluated.