The effects of oral contraceptives and parity on ovarian cancer trends in women under 55 years of age.

ABSTRACT

Mortality from epithelial ovarian cancer is falling in women under 55 years of age in England and Wales. The decline does not appear to be a treatment effect nor to be attributable to changes in the rate of oophorectomy. Case-control studies have shown that high parity and oral contraceptive use are protective against the disease. We suggest that the decrease in mortality is compatible in timing and magnitude with exposure to oral contraceptives. No obvious effect on mortality attributable to parity was apparent in this analysis. Oral contraceptives may prove to be a widely acceptable means of preventing ovarian cancer, providing they do not increase breast cancer risk.

ABSTRACT

PIP Age-specific mortality and incidence data for each calendar year (between 1950-86 for mortality and 1971-84 for incidence) were obtained from the Registrar General's Statistical Review for England and Wales and the Office of Population Censuses and Surveys publication series to consider whether the hypotheses generated by case-control studies on the effects of parity and oral contraceptive (OC) use are compatible with ovarian cancer trends in England and Wales. Rates were calculated on the basis of the mid-year female population within each 5-year age group. Initial examination of the data showed that the age-adjusted mortality rate from ovarian cancer for all women over 25 increased considerably between 1950-70 but changed little thereafter. The decline did not appear to be a treatment effect nor to be attributable to changes in the rate of oophorectomy. Case control studies have shown that high parity and OC use are protective against ovarian cancer. The disease in mortality emerges as compatible both in timing and magnitude with exposure to OCs. Ocs may prove to be an effective and widely acceptable means of preventing ovarian cancer, as long as they do not increase the risk of breast cancer.