Reproductive Risk Factors for Epithelial Ovarian Cancer According to Histologic Type and Invasiveness

PURPOSE: Differences in histology among the subtypes of epithelial ovarian tumors suggest possible differences in their etiologies. We examined reproductive risk factors for epithelial ovarian cancer according to histologic subtype and tumor invasiveness. METHODS: We conducted a population-based, case-control study of associations between reproductive risk factors and epithelial ovarian cancer in the Delaware Valley from 1994 to 1998. Cases age 20 to 69 years with a recent diagnosis of epithelial ovarian cancer (n = 767) were compared to community controls (n = 1367) frequency matched by age. RESULTS: With few exceptions, we found significant risk reduction for each histologic subtype of epithelial ovarian cancer by using oral contraceptive, bearing children, and having a tubal ligation; for each subtype, there was significant increased risk associated with a family history of the disease. There were no significant differences among histologic subtypes in the magnitude of the odds ratios for OC use, parity, breastfeeding, tubal ligation, hysterectomy, family history of breast or ovarian cancer, use of noncontraceptive estrogens, age at menarche, and age at menopause. There were also few differences between invasive and borderline tumors, except that women with borderline tumors were significantly younger than women with invasive disease (44.7 years vs. 52.0 years, p < 0.001). Among serous tumors only, women with borderline tumors were more likely to use oral contraceptives than women with invasive tumors (OR = 2.28 95% CI 1.20–4.35). CONCLUSION: The results of this study suggest that reproductive risk factors do not differ among histologic subtypes of epithelial ovarian cancers.