Around 1% of women in northern Europe and the USA are at risk of ovarian cancer before 70 years of age; the risk is smaller in other developed countries and in less-developed settings. Previous research has suggested that women with breast cancer have a small increased risk of ovarian cancer; this risk is greatly increased in the presence of specific gene mutations (BRCA1 AND BRCA2). However, these gene mutations do not account for all familial breast or ovarian cancers, which (combined with the absence of genetic screening programmes) suggest that other factors--for example the age at onset of breast cancer, and information about a family history of breast or ovarian cancer--might be more useful to identify women with breast cancer at the greatest risk of ovarian cancer.
Kjell Bergfeldt and colleagues from the Karolinska Institute, Stockholm, Sweden, identified over 30,000 women under 70 years of age who had been diagnosed with breast cancer. The investigators obtained information about breast cancer and ovarian cancer for around 146,000 first-degree relatives (parents, siblings, children) of the study population.
After an average of six years follow-up, women with breast cancer were twice as likely to have ovarian cancer than women in the general Swedish population. Diagnosis of breast cancer before 40 years of age substantially increased the risk of ovarian cancer. Women with breast cancer who did not have a family history of either breast or ovarian cancer had a 60% relative increase in risk of ovarian cancer compared with the general population. Women with a family history of either disease were at a much greater risk of ovarian cancer than the general population (five to sixfold increased risk for a family history of breast cancer, and a seventeen-fold increased risk for a family history of ovarian cancer).
Kjell Bergfeldt comments: "The clinical implications of our findings are not obvious, especially because there is no effective screening strategy for ovarian cancer. However, provided that our results are confirmed by other investigators, they seem to allow identification, based on easily obtained clinical information, of a small subgroup of women with breast cancer who are at particularly high risk of ovarian cancer. In this subgroup, counselling, and perhaps even prophylactic oophorectomy, might be considered."
Contact: Dr Kjell Bergfeldt, Department of Medical Epidemiology, Karolinska Institute, Box 281, S-171 77 Stockholm, Sweden; T) +46 8 517 70000; M) +46 70 626 56 19; F) +46 8 314 975; E) Kjell.Bergfeldt@mep.ki.se