The epidemiology of ovarian cancer.

Although no unequivocally effective ovarian cancer prevention strategies have emerged, epidemiologic studies have identified high-risk populations. The striking international variation (apparently a fivefold difference) can probably be explained on the basis of differential parity, differing classification measures, and differences in the underlying population age distribution. United States age-adjusted mortality has increased slightly in the past 30 years, and the cancer remains predominantly a disease of older adult white women of northern European extraction. The increases in age-specific mortality and age-adjusted mortality over time may be related to a decrease in average family size. Pregnancy, especially pregnancy before age 25 years, and use of oral contraceptives are protective; the risk of ovarian cancer increases with increasing years of ovulation. A positive family history is also associated with a substantial increase in ovarian cancer risk. Survivors of ovarian cancer are more susceptible to cancers of the breast, endometrium, and colon than are similarly-aged normal women, most probably because all four cancers share some common risk factor(s). Various alkylating agents are clearly leukemogenic in survivors of ovarian cancer, an observation that suggests caution in the use of adjuvant chemotherapy in women at relatively low risk of relapse.