Reproductive and hormonal factors and ovarian cancer.

BACKGROUND Menstrual, reproductive and hormonal factors have been related to ovarian cancer risk, but further quantification of their role in various populations is required. PATIENTS AND METHODS Cases were 1031 women, below age 79, with incident, histologically confirmed epithelial ovarian cancer, and controls 2411 women, admitted between 1992 and 1999 to a network of hospitals in 4 Italian areas for acute, non-neoplastic, diseases. Odds ratios (OR) were obtained using multiple logistic regression. RESULTS Multiparity was associated with a significant reduction in risk of ovarian cancer (OR = 0.6 for 3, and 0.5 for > or = 4 births). No consistent association was observed with time since first or last birth, nor with spontaneous or induced abortions. Late age at menarche (OR = 0.8), and early menopause (OR = 0.6) were inversely related to risk, as did long-term oral contraceptive use (OR = 0.5, for > or = 5 years). Hormone replacement therapy in menopause was associated with a non-significantly elevated risk (OR = 1.4). The pattern of risk was similar for women with and for those without family history of breast or ovarian cancer. CONCLUSIONS This uniquely large study confirms and further quantities the relation between hormonal and reproductive factors and ovarian cancer. The pattern of risk observed cannot be totally explained by a role of ovulation in ovarian carcinogenesis.