Family History and Inherited Cancer Susceptibility
Certain common, chronic disease predispositions are inherited in families. Individuals who have a family history of cancer in close relatives are more likely to develop the disease. The person's risk increases when there are more affected relatives, and if the disease was diagnosed at an early age.
All healthcare providers, including nurses, collect family history information. Family history is an important and powerful screening tool that can help identify at-risk individuals for whom specific clinical risk-management interventions would be beneficial. For example, certain specific family history patterns are associated with an increased likelihood for mutations in the BRCA1 or BRCA2 genes that predispose individuals to breast/ovarian and other cancers. For all hereditary cancers, collecting family history from both the mother's and father's side of the family is needed to assess risk, because inherited risk for any cancer can come from either side.
People who are identified as being at increased risk can be advised to make specific lifestyle changes and initiate cancer screening at an earlier age, sometimes with greater frequency and using different modalities. Referrals of high-risk individuals and families can be made to a specialist for further assessment of genetic/genomic risk factors.
In recognition of the importance of family history, the US Surgeon General developed My Family Health Portrait, a computerized tool to facilitate collection of data about family history. Using the Family Health Portrait, individuals can enter their own family health history information and create diagrams of their family health history (pedigree) to share with their family members and healthcare provider. Screening and risk-management guidelines based on family history are now available for many common diseases, including cancer. Evidence regarding the effectiveness of these strategies for high-risk individuals is growing. Consistent with the Essentials of Genetic and Genomic Nursing, nurses at all levels of practice should be competent in constructing a pedigree from the collected family history information using standardized symbols and terminology.
In addition to using family history to screen for hereditary diseases, genetic testing is used to identify and clarify levels of risk more precisely, to inform healthcare decisions. Genetic testing is available to individuals at risk for hereditary, early-onset diseases such as breast and colon cancer, as well as many other cancers. Furthermore, men and women who present with a family history of early-onset breast and ovarian cancer or with early-onset disease may be candidates for genetic testing for mutations in the BRCA1 and BRCA2 genes. Mutations in BRCA1 or BRCA2 are highest in families who have a number of family members affected with breast and/or ovarian cancer. Mutations in BRCA1 and BRCA2 also increase the risk for cancers of the pancreas, melanoma, and other malignancies.
Gene-Based Cancer Diagnostics
Genetic testing was originally used to diagnose genetic disorders in infants and children born with birth defects suggesting a genetic condition, such as Down syndrome. As genetic and genomic research has expanded, genetic testing is now being used for diagnosis and prognosis of, as well as therapy decision-making for, common diseases like cancer. Both chromosome analysis and gene-based studies can contribute to the diagnosis and management of patients with cancer.