Genetic Testing for Cancer

Both germline mutation and somatic mutation can play key roles in causing cancers. Genetic tests help reveal mutations that may relate to the occurrence of cancers, hence, to understand the diagnosis, treatment, and prevention strategies of the disease.

Genetic tests can be used in different ways related to cancers. For example, some tests reveal germline mutations in healthy individuals for cancer risk prediction, while some reveal somatic mutations in cancer patients for matching cancer therapy as well as deciding the appropriate targeted drugs or immunotherapies. Let’s find out what hereditary cancer is about!

Genetic Testing for Hereditary Cancer Risk: What are Germline mutations?

Germline mutations are variants inherited from birth and they can exist in every body cell. A predictive genetic test can evaluate the lifetime risk of having specific cancer by identifying the inherited germline mutations.

Understanding Familial Risk for Cancer:

According to National Cancer Institute in the US, knowing if a person has a cancer predisposing gene mutation may help prevent, diagnose, and treat cancer1. In terms of genetic contribution, breast, bowel, stomach and prostate cancer among all cancer types can be strongly influenced by genes and can run in families2, ranging from 10 to 20%3.

For high-risk groups (people with a strong family cancer history), a predictive genetic test can help determine if they carry a gene mutation linked to a higher lifetime risk of developing certain types of cancer. For people having family members known to have an inheritable gene mutation, the tests can reveal if they carry the same genetic mutation. Healthy individuals with positive test results (which means carrying an inherited gene mutation) can consider starting corresponding cancer screening as soon as possible and screening more frequently. With genetic information on hand, individuals can consult medical professionals to plan for cancer preventative treatments to intervene before cancers occur. Other than that, individuals can make certain lifestyle changes to lower the cancer risk.

For people already diagnosed with cancer, testing for germline mutation can check if cancer might have been caused by an inherited mutation within the family which can be beneficial to the patients’ treatment as well. For example, patients with higher-risk forms of BRCA1/2 mutations associated with inherited breast cancer, ovarian cancer, pancreatic cancer and prostate cancer are highly sensitive to 3 FDA-approved PARP inhibitors. On top of that, the result may help their family members to consider their need to take a genetic test.


  1. National Cancer Institute. Cancer predisposing gene mutation. Available at:
  2. NHS. Predictive genetic tests for cancer risk genes. Available at:
  3. Samadder, N. J., Riegert-Johnson, D., Boardman, L., Rhodes, D., Wick, M., Okuno, S., Kunze, K. L., Golafshar, M., Uson, P. L., Mountjoy, L., Ertz-Archambault, N., Patel, N., Rodriguez, E. A., Lizaola-Mayo, B., Lehrer, M., Thorpe, C. S., Yu, N. Y., Esplin, E. D., Nussbaum, R. L., … Stewart, A. K. (2021) ‘Comparison of Universal Genetic Testing vs guideline-directed targeted testing for patients with hereditary cancer syndrome’, JAMA Oncology, 7(2), pp. 230.