Genetic testing can have implications for management of the cancer patients, including: surgical treatment, chemotherapy choices, prognosis and risk for additional cancers. It is therefore important to assess the risk of a hereditary syndrome at diagnosis, at decision points along the cancer treatment trajectory and again when entering survivorship or surveillance. An exhaustive list of implications of all cancer predisposition syndromes or germline alterations is beyond the scope of this toolkit; however we will provide some of the more common implications of identification of germline mutations in patients with cancer.

Genetic testing of a cancer assesses somatic genetic changes that may guide therapeutic choices (e.g., EGFR mutations for treatment of lung cancer). Some tumor (somatic) genetic testting will include mutations potentially inherited (germline) as well as those acquired in the tumor (somatic). Other genetic tests of the tumor will "subtract out" germline mutations by comparing mutations in the tumor to those found in sample of normal tissue or blood. It is important to understand which approach the genetic test you are reviewing has used. This toolkit does not address tumor somatic mutations. Germline genetic testing, usually performed on a blood sample, evaluates inherited genetic changes that increase the risk of certain cancers in an individual.

Benefits of Germline Genetic TestingGenetic testing can help identify cancers for which an individual is at increased risk. This increased risk can often be managed by increased surveillance, consideration of preventive medication or prophylactic surgery. In addition, identification of a familial germline mutation in a cancer susceptibility gene can alert family members who would also undergo genetic testing to clarify their own risk of cancer. Finally, identifying certain germline mutations may guide local and systemic treatment of a cancer (e.g., colectomy for a patient with colorectal cancer and Lynch syndrome; PARP inhibitor for a patient withovarian cancerwith aBRCA1/2mutation; avoidance of therapeutic radiation in a patient with breast cancerwith inheritedTP53mutation).

Germline mutations and second cancer risk: Second primary cancers occur in approximately 16% of all patients with cancer. Those individuals with strong family histories and/or pathogenic germline mutations in cancer-causing genes are at highest risk of second primary cancers. Genetic testing during survivorship or surveillance can identify those at greatest risk and action (more intense screening or preventive surgery) can be taken.

The guidelines below represent a selection of publicly available resources on genetic testing for specified cancer syndromes; this list is not exhaustive due to restrictions of member-only content. **Inclusion of third-party guidelines and recommendations should not be interpreted as formal endorsement by ASCO.**

Breast and Ovarian Cancer

Colorectal Cancer

Other Topics

Counseling

Heredity Diffuse Gastric Cancer

Medullary Thyroid Cancer

von Hippel-Lindau Syndrome

Comments or Questions?Please contact us atPrevention@asco.org

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Genetic Testing | ASCO

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