B37
Age of onset in hereditary and familial breast cancer
Andreas Brandt1, Justo Lorenzo Bermejo1, Jan Sundquist2, Kari Hemminki1
1German Cancer Research Center (DKFZ), Heidelberg, Germany, 2Lund University, Malm, Sweden
Background
A family history is associated with an increased risk of breast cancer. When it includes early onset or bilateral breast cancers and multiple cases of breast or ovarian cancers, it is a strong predictor of hereditary breast cancer. Hereditary breast cancer is associated with an earlier age of onset. One aim of this study was to determine how many years earlier women whose family history indicates a risk of hereditary breast cancer reach the cumulative risk of women lacking a family history. However, most women with affected relatives do not fulfil high-risk criteria. Therefore, the second aim was to derive the corresponding data for women with a mother or sister affected by breast cancer.
Method
The nation-wide Swedish Family-Cancer Database includes 11.8 million individuals and 144,000 cases of breast cancer diagnosed from 1958-2006. Women in the Database were grouped according to seven criteria that are applied in clinical practice to identify high-risk women. Cumulative risks of breast cancer were estimated with a stratified Cox model according to the criteria. For women with a mother or sister affected, cumulative risks were calculated according to the diagnostic age of the relative.
Results
The age to reach the same cumulative risk as women without family history at age 50 ranged from 32 to 41 years in women from high risk groups. For women with affected mother or sister, this age was decreasing with decreasing diagnostic age of mother or sister, ranging from 38 years (mother affected < 40 years) to 47 years (sister affected 60-72 years).
Conclusion
Current recommendations on the earlier starting age of screening among high risk women, based on expert opinions, appear largely justified. The present data on the onset age of familial breast cancer outside high-risk groups should encourage further analysis in order to derive evidence-based recommendations.
