Genetic testing of cancer predisposition

Cancer is a multistep process determined by the occurrence of sequential genetic changes in cells of the somatic Lineage. A minority of cancer patients present with a striking tumor family history, suggestive of mendelian inheritance. It has been shown that specific familial cancer aggregations are due to mutations in cancer-predisposing genes which are transmitted through the germline. So far, more than 20 genes associated with cancer predisposition have been identified. Since the genes involved are many, currently there is no universal test for cancer predisposition. Rather, mutation detection strategies need to be tailored according to the type of gene which needs to be investigated. This is established based on clinical evaluation, on analysis of clinical documentation, and on pedigree reconstruction and interpretation. Therefore, genetic counseling is a fundamental step of cancer genetic testing. The counseling process includes also the provision of adequate information on the limits of cancer genetic tests, on the risks associated with mutations in specific genes, and on the options available for prevention and early diagnosis. Due to the complexity of these issues, scientific and professional organizations usually recommend that genetic tests for cancer predisposition be performed in institutions actively involved in research in the field. To better handle the multiple facets of familial cancer syndromes, ad hoc multidisciplinary teams ("cancer family clinics") have been established in a number of countries. While the bulk of knowledge accrued so far concerns clearcut hereditary conditions associated with high penetrance, there are growing data indicating that less penetrant mutations, and even common polymorphisms, are involved in cancer susceptibility, albeit with lower risks. Further discoveries in the field will probably lead to an exponential increase in the number of potential candidates to genetic tests. However, before these can be applied on a population scale, there is a need for improvements and standardization of management and surveillance strategies.