Although first-degree relatives of women with breast cancer (mothers, sisters, daughters) are at increased risk of the disease, most women who develop breast cancer do not have an affected relative, report researchers from Oxford in this week's Lancet.
These workers also show that the more affected relatives a woman has, the more likely she is to develop the disease. Understandably, this risk is of concern to both parties. Previous studies have not been sufficiently large accurately to identify the size of the risks.
An analysis published this week in The Lancet combines the results of studies already done and comes up with detailed estimates of the risks of developing breast cancer at various ages. One finding is that the number of affected relatives is more important that the age the relatives were when their cancers were diagnosed.
Members of the international Collaborative Group on Hormonal Factors in Breast Cancer (whose members are listed on The Lancet website www.theLancet.com) combined the results of 52 separate studies, and in total compared the risks of breast cancer in first-degree relatives in 58,209 women with breast cancer with the risks in 101,986 women without breast cancer. They found that the lifetime incidence of breast cancer for women with one affected relative was 7.8%; for women with two affected relatives, 13.3%; and for women with three affected relatives, 21.1%. The risk was the same whether mother or daughter were affected; and that risks were greater in older than in younger women.
The authors of the report firmly put these findings in proportion, “Eight of nine women who develop breast cancer do not have an affected mother, sister, or daughter. Although women who have a history of breast cancer are at increased risk of the disease, most will never develop breast cancer, and those who do will be over 50 when their cancer is diagnosed.”
Contact: Professor Valerie Beral ICRF Cancer Epidemiology Unit, Gibson Building, Radcliffe Infirmary, Oxford OX2 6HE, UK; T) +44 (0) 207 269 3141; F) +44 (0) 207 269 3262; E) pressoffice@imperialcancer.co.uk
Journal
The Lancet