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Cancer gene discoveries have led to important changes in the clinical practice of cancer risk assessment. Genetic tests, in conjunction with family history information, can be used to a) clarify the diagnosis of inherited cancer syndromes in patients with tumors and b) provide information about cancer susceptibility to asymptomatic persons in high-risk families. The promise of cancer gene testing is reduced cancer incidence and mortality through directed prevention and screening.
In addition to the medical and health benefits of cancer gene testing, the power to identify high-risk persons has led to considerable discussion of the implications from consumer, epidemiologic, technologic, ethical, legal, policy, psychological, and genetic counseling perspectives.
Cancer gene testing can include a variety of modalities, including linkage, direct detection when the mutation is known, and mutation analysis, such as protein truncation test or sequencing. In addition, tests for microsatellite instability in colon tumors and gene expression assays may provide indirect evidence supporting a diagnosis of hereditary nonpolyposis colorectal cancer.
Commercial availability of germline cancer gene tests (i.e., BRCA1, BRCA2, APC, hMSH2, hMLH1, p16, NF2) has outpaced the awareness among health professionals of the need for careful implementation of testing algorithms and patient education on the issues.
Surveys of persons at varying risks for cancer show that most persons are interested in having a gene test. The actual uptake of cancer gene testing has been more modest; the decision to undergo gene testing is influenced by psychosocial factors, including perception of cancer risk, perceived ability to cope with gene test results, depression, and fear of insurance discrimination. Among persons who are tested, there appears to be no significant short-term (1–3 months) psychological distress following disclosure of results.
Cancer genetic risk assessment is a multistep process and incorporates medical, psychological, genetic, and counseling dimensions. Clinical indications and a model algorithm for cancer risk assessment and gene testing are provided. For persons who are at risk for cancer, gene test interpretation will depend upon whether the specific germline cancer gene mutation is known for the family. Careful evaluation of the pedigree for characteristic aggregation of tumor types among affected individuals and availability of affected persons for testing are important issues in implementing genetic testing.
Health professionals will need to be aware of the variety of issues that contribute to the process of helping patients to understand their risk, make informed decisions, and appreciate the implications for cancer prevention and risks for other family members. Genetic counseling is an essential component of cancer genetic risk assessment services.
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The translation of cancer gene discoveries into the clinical setting by the introduction of genetic testing has undergone a remarkable evolution in a few short years. Cancer genetic testing has become a significant focus from a variety of perspectives because it represents a potentially powerful means to identify high-risk individuals. From a medical and public health perspective, cancer genetic testing provides a more precise way to intervene ...