Risk of breast cancer in relation to the use of rauwolfia alkaloids.

In a case-control study of 1881 women with breast cancer and 1523 controls with benign conditions, 65 cases (3.5%) and 64 controls (4.2%) reported having used a drug that contained rauwolfia, giving a rate ratio estimate of 0.8 (95% confidence interval, 0.5-1.1). Use that ended more than a year previously was negatively associated with breast cancer (rate ratio, 0.5; 95% confidence interval, 0.2-0.9). The risk of breast cancer did not vary significantly according to duration of use. Nor did it vary within strata of varying base-line risk, such as age at first pregnancy. The data suggest that rauwolfia alkaloids do not increase the risk of breast cancer.