Gene-environment effects
The smaller contributions of many genes throughout the genome are
thought to explain population
cancer risk, together with environmental factors such as hormone
exposure, smoking and aging \cite{Cronin_2018}. At the population level, about 18% of the
familial relative risk of breast cancer can currently be explained by
mostly common variants identified by
genome wide association
studies \cite{Michailidou_2017}. Using these variants for polygenic prediction, the 1% of
women with the highest predicted genetic risk would have a 3.5-fold
(42% lifetime risk) compared to the population average (12% lifetime
risk). Such tests are undergoing clinical investigation for their
utility in prioritizing early detection and prevention strategies,
particularly for those with sparse or unrecorded family history of
cancer.