Summary

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  • Three groups of genes are involved in the development of cancer:

    • Oncogenes function as proto-oncogenes to promote normal cell growth; a deleterious mutation in a proto-oncogene causes the gene to become an oncogene. Oncogenes cause cancer by becoming more active or gaining an additional function, resulting in more rapid cell growth.

    • Tumor suppressor genes normally function to regulate the timing of cell growth and division. A mutation in a tumor suppressor gene causes cancer by reducing the gene's normal activity or eliminating its function entirely, allowing for uncontrolled cell growth.

    • DNA repair genes are responsible for repairing genetic informationl; a mutation in a DNA repair gene may allow inaccurate genetic information to be passed onto daughter cells. Mutations in DNA repair genes lead to cancer by allowing mutations to accumulate in the genome (including mutations in proto-oncogenes and tumor suppressor genes), eventually leading to uncontrolled cell growth.

  • For sporadic and heritable cancer to develop, a multistep sequence of events must take place. This sequence is best described by Vogelstein's hypothesis.

  • One of the best ways to detect persons at risk for heritable cancer(s) is to take a detailed, 3-generation family history. It is important to remember that not all people with heritable cancers have a significant family history. Pedigrees should include the following:

    • ethnicity
    • maternal and paternal family members
    • detailed personal and family cancer history
    • presence of any noncancer health findings or unusual physical features
    • description of any environmental carcinogenic exposures
    • any previous genetic test results
  • When comparing characteristics of sporadic cancers to heritable cancers, hereditary cancers more commonly

    • occur at younger ages
    • affect both sides of the body
    • cause multiple types of cancer in the same person
    • cause rare forms of cancer
    • affect multiple family members
    • display an autosomal dominant pattern of inheritance
  • Patients without cancer, but who are at increased risk for hereditary cancer(s), are usually managed with increased surveillance. Depending on the particular cancer syndrome, many patients are also offered prophylactic surgery, medications, and appropriate lifestyle changes as additional options.

  • Patients with heritable forms of cancer are often offered treatment options similar to patients with sporadic cancers. Occasionally, however, individuals with heritable cancers do need to be treated differently.

  • Many professional and patient resources are available online. Two popular professional websites include
    NCI and GeneTests. The NCI website also hosts extensive patient materials.