Different Risk Factor Profiles for Mucinous and Nonmucinous Ovarian Cancer: Results from the Danish MALOVA Study

Abstract

The aim of the study was to examine the overall risk factors for epithelial ovarian cancer and according to histologic subtypes. Ovarian cancer cases and controls were recruited from 1995 to 1999, and personal interviews were conducted. A total of 554 cases and 1,564 randomly selected controls were included. The analyses were done using multiple logistic regression models. The overall risk of ovarian cancer decreased with ever being pregnant [odds ratios (OR), 0.40; 95% confidence intervals (CI), 0.30-0.55], with increasing pregnancies (OR, 0.63; 95% CI, 0.45-0.87 and OR, 0.51; 95% CI, 0.37-0.69 for two and three pregnancies as compared with one), and with older age at first and last pregnancy, respectively. Increasing years of ovulation was a very strong risk factor with a 7% to 8% increase in risk for each year of ovulation. Use of oral contraceptives (OR, 0.67, 95% CI, 0.53-0.85) and longer duration of use were associated with a decreased risk of ovarian cancer. Ever use of hormone replacement therapy increased the overall risk (OR, 1.30; 95% CI, 1.05-1.61). For all those variables, the effect was present for serous tumors, endometrioid tumors, and tumors of other histologies, but not for mucinous tumors. In contrast, current smoking was a risk factor only for mucinous tumors (OR, 1.78; 95% CI, 1.01-3.15) and increasing body mass index tended to increase the risk especially for mucinous and endometrioid tumors. We confirmed already known risk factors for ovarian cancer, and we observed significant differences in the risk profiles between mucinous and nonmucinous tumors indicating different etiologies.