ABSTRACT
Since the relationship between oral contraceptive use and breast cancer had not been consistent, the authors undertook a meta-analysis of studies published to date. Papers were located by searching the MEDLINE database, supplemented by a hand search of all the references in the articles recovered. Studies were graded as to quality. Those judged as probably unbiased were included in the analysis. The method of Woolf was used to combine relative risks. Forty-seven studies were collected: 40 case-control and 7 cohort studies. Thirty-nine of these were considered unbiased. The main results observed were that the relative risk was 1.06 (1.02-1.10) for all studies and 1.14 for premenopausal cancer. For premenopausal cancer, higher relative risks were observed in women who early used oral contraceptive with a significant linear dose-response effect: 1/25 (1.10-1.44) in oral contraceptive users before age 25, and 1.17 (1.06-1.30) in users before the first full-term pregnancy. The authors concluded that oral contraceptive use may be a risk factor for premenopausal breast cancer.
