Population attributable risk for ovarian cancer.

Parity, oral contraceptive (OC) use, age at menopause, a family history of the disease and selected aspects of diet have been related to the risk of ovarian cancer. The quantification of their impact on a population level may help focus and rank the importance of potential prevention strategies. Using data from a case-control study conducted in Italy between 1983 and 1991 on 971 ovarian cancer cases and 2758 control women we computed the multivariate relative risk estimates, and population attributable risks (PARs), i.e. the proportion of ovarian cancers that would have been avoided if a given exposure had not been present in the population. Overall, the PARs were 5% for nulliparity, 12% for never OC use and 4% for a family history of breast or ovarian cancer in first-degree relatives. Among women aged >/=50 years, later age at menopause accounted for 16% of all ovarian cancer cases. Low intake of green vegetables accounted for 24% of cases and a high fat score for 7%. All these factors together explained 51% of cases. In conclusion, even if the PAR estimates were based on several arbitrary assumptions, available knowledge could, in principle, explain over 50% of all ovarian cancer cases in this Italian population, thus indicating and quantifying the theoretical scope for prevention.