Familial ovarian carcinoma

Segregation analysis of epithelial ovarian cancer in Finland

Epithelial ovarian cancer is known to aggregate in families. The dominantly inherited ovarian cancer predisposing genes, BRCA1, BRCA2 and genes involved in the hereditary non-polyposis colorectal cancer (HNPCC) syndrome, have recently been identified. However, in the majority of families with more than one case of ovarian cancer, dominant inheritance cannot be recognized. We investigated familial clustering of epithelial ovarian cancer in a population-based sample of 663 Finnish ovarian cancer patients. A segregation analysis with the POINTER software was conducted on the 937 nuclear families from these 663 pedigrees. The major gene model was favoured, and the sporadic and multifactorial models were strongly rejected. In the studied population, the best fitting model was a recessive mode of inheritance, and 8% of ovarian cancer patients were estimated to be homozygous for the deleterious genotype. This evidence for recessively inherited ovarian cancer predisposition should be interpreted cautiously, as the analysis is subject to certain errors, which are discussed in the article. Results of this analysis, however, strongly emphasize the role of genetic factors in all familial aggregation of epithelial ovarian cancer.

Cancer incidence in the first-degree relatives of ovarian cancer patients

Cancer incidence was studied among 3072 first-degree relatives of 559 unselected ovarian cancer patients. Among cohort members there were 306 cancer cases. The overall cancer incidence was not increased: the standardised incidence ratio (SIR) in males was 0.9 (95% confidence interval 0.8-1.1) and in females 1.0 (0.8-1.1). The female relatives had a significantly increased risk for ovarian cancer (SIR 2.8, 1.8-4.2). The excess was attributable to sisters only (SIR 3.7, 2.3-5.7). The relative risk for ovarian cancer among sisters decreased both by increasing age of the sister and by increasing age at diagnosis of the index patient: the SIRs were 7.3 (1.5-21.4), 4.5 (1.6-9.8) and 3.1 (1.7-5.4) for sisters of index patients diagnosed in age < 45, 45-54 and 55-75 years respectively. The age dependency of the risk supports the role of genetic factors in familial ovarian cancer. Although the risk of ovarian cancer among sisters from families with breast cancer (SIR 9.2, 3.7-19.0) was significantly higher than among sisters from families with no breast cancer patients (SIR 2.9, 1.6-4.8, rate ratio 3.1, P < 0.05), the excess was not solely attributable to coaggregation of breast and ovarian cancer. Among the 27 families with two or more ovarian cancers, only sisters were affected in 24 families, which might implicate recessive inheritance or shared environmental factors influencing ovarian cancer risk in sisters.

Ovarian dysplasia. A study of identical twins

The normal, identical twin sisters of patients who had been the subjects of ovarian cancer were subjected to prophylactic oophorectomy after the menopause. The finding of epithelial abnormality suggests a precancerous change similar to other genital epithelial dysplasia.