Cancer Genetics 101

Inherited Risk of Cancer

Some changes to your DNA are known to increase your risk of developing certain types of cancer. These DNA changes are usually found in all tissues in the body and can be passed along to your children. Using molecular tests like DNA sequencing on normal tissue (such as blood or saliva) can determine if a person has one or more of these known DNA changes that are genetic risk factors, and can therefore assess risk for developing particular cancers, decide to initiate a screening program, or help choose a targeted or proven medication. 

Some examples include Lynch syndrome (an inherited predisposition to developing colorectal cancer or endometrial cancer, in addition to other types of cancers, due to changes in genes that are involved in DNA repair) and susceptibility to developing breast, ovarian, pancreatic, and prostate cancers due to changes in the BRCA1 or BRCA2 genes

Testing to determine inherited predisposition to cancer is known as germline testing, genetic testing, or inherited disease testing.


Cancer Biomarkers

While some DNA changes are found in all tissues of a patient's body, cancerous tissues and tumors frequently have specific DNA changes, sometimes called “somatic mutations”. These changes are found in cancerous tissues and are referred to as biomarkers, they can include mutations and other genetic changes. 

Determining if a patient has one or more of the known biomarkers can help inform diagnosis, directed therapy (such as specific drugs or immunotherapies), prognosis, clinical trial eligibility, and patient management. Some biomarkers may not currently have an associated therapy and other treatment options may be more appropriate. 

A patient can be tested for biomarkers through molecular laboratory tests, such as DNA sequencing, performed on a sample of cancerous tissue take from a biopsy. 

Some examples include testing of non-small cell lung cancers (NSCLC) to effectively guide targeted therapy and identifying chronic myeloid leukemia (CML) patients who would benefit from treatment with specific tyrosine kinase inhibitors, such as imatinib. 

Testing to determine a patient's biomarker status is known as cancer biomarker testing, cancer genetic testing, molecular testing or tumor profiling. 

Generally, most biomarkers are found only in the cancerous tissue and are not passed along to the person's children. However, sometimes a person will have a DNA change throughout all the tissues of their body that makes them more likely to develop cancer AND specific DNA changes that only occur in the cancerous tissue. In this case, a full “biomarker profile” for this patient would include both classic biomarkers and any genetic risk factors for developing cancer.


Genetic Testing for Cancer

Currently, there are a diverse array of cancer biomarkers that are known to affect diagnosis, predict response to directed therapies (such as an FDA-approved immunotherapy), determine prognosis, inform clinical trial eligibility and impact patient management. These biomarkers can be assessed by many different techniques, including nucleic acid testing, in addition to protein-based assays or other types of analytes. Some examples of tests used to assess a person's biomarkers are below. Please note that this is not an inclusive list and each type of test is not appropriate for all types of cancer. Some of these tests can also be used to determine a person’s inherited risk of cancer.

Disease-Specific Biomarkers

Please note that we are constantly updating this list of resources! If you have a biomarker-based resource that you would like to recommend for inclusion, we invite you to contact us here