Oral contraceptives and ovarian cancer: an update, 1998-2004.

Over the last two decades, ovarian cancer incidence and mortality for younger generations have been declining in most developed countries, and the decline has been greatest in countries where oral contraceptive (OC) use had spread earlier. The overall estimated protection from cohort and case-control studies is approximately 30% for ever OC users, and increases with duration of use by approximately 5% per year of use to about 50% for long-term (> or =10 years) users. The favourable effect of OC against ovarian cancer risk persists for at least 20 years after OC use has ceased, and it is not confined to any particular type of OC formulation. The reduced risk among OC users is observed in women without or with family history or genetic predisposition to ovarian cancer, and for most histological types of epithelial ovarian cancer, although the pattern of risk is less consistent for mucinous than for other types. The protection of OC on ovarian cancer risk, also in view of its long-term persistence, corresponds to the avoidance of 3000-5000 ovarian cancers (and 2000-3000 deaths) per year in Europe, and a similar figure in North America.