Risk of ovarian cancer and genetic relationship to other cancers in families.

The risk of ovarian and other cancers was assessed in first-degree relatives of patients with ovarian cancer from an analysis of 391 pedigrees. Overall there was a significant increase in the risk of ovarian cancer (4.5-fold; p < 0.001). The risks were 14.2- (p < 0.001), 5.2- (p < 0.001) and 3.7-fold (p < 0.001) for relatives of patients diagnosed before 45, between 45 and 54 and after the age of 55, respectively. There was no significant increase in the risk of cancers of the uterus, stomach, lung, colorectum or prostate. There was, however, an overall increase in the risk of breast cancer (1.3-fold; p < 0.05). The risk was highest for those relatives of patients diagnosed with ovarian cancer before the age of 55 (2.2-fold; p < 0.01). These results support the role of genetic factors in the aetiology of ovarian cancer and provide further evidence for the existence of a breast-ovarian family cancer syndrome, which may result from the pleiotropic effects of the same gene in some families.