Effect of genome-wide association studies, direct-to-consumer genetic testing, and high-speed sequencing technologies on predictive genetic counselling for cancer risk.

Genetic counselling is offered to patients with various hereditary cancers. At-risk family members can be identified by predictive testing and included in specifically designed screening and prevention programmes. Since genetic testing has far-reaching ethical and medical outcomes, it is usually done according to well-defined guidelines developed by medical societies, entailing extensive interaction between family members and medical health providers. This established procedure is now changing after three new developments. First, data from genome-wide association studies have identified many new loci in the human genome, which could moderately change cancer risk. Second, although inclusion of low-risk cancer genes in patients' risk assessments represents an unresolved challenge, several companies already offer such tests in a direct-to-consumer format over the internet. These tests shift control of genetic testing from medical professionals to individuals. Third, development of high-speed sequencing technologies multiplies available genomic data and enables rapid sequencing of entire human genomes at low costs. This innovation will pave the way for personalised genetics and new options for predictive testing. Here, we use the example of genetic counselling in colon cancer to describe how these developments will change genetic testing in families at risk of cancer and in the general population.