A case-control study of breast cancer in relation to the use of steroid contraceptive agents.

In a case-control study of 141 cases of breast cancer and 279 control patients from the Royal Prince Alfred and Westmead Hospitals during 1980-1982, we found similar risk factors to those reported for other populations. There was no statistically significant evidence of an increased risk of cancer from the use of oral contraceptive agents; the crude estimate of relative risk for patients who had used oral contraceptive agents at some time was 1.3 with 95% confidence limits of 0.8 and 1.9. After adjustment for other risk factors (age at first live birth, age at menarche, number of pregnancies, menopausal status, bilateral oophorectomy and years of education), the estimate of the relative risk of ever having used an oral contraceptive agent was 0.9 with 95% confidence limits of 0.6 and 1.5. Further analysis in terms of duration of use and dosage also provided no evidence of an increased risk.