Sheila Rajagopal, MD, MSc, MPH
The following question was addressed by Sheila Rajagopal, MD, MSc, MPH, a board-certified medical oncologist and bioinformatician, who recently joined us at Vanderbilt University Medical Center.
Q: In people with hereditary cancers, why might genetic testing in the tumor be important to guide treatment?
A: You may hear about two types of “genetic testing” – (1) testing for inherited cancer risk, which uses saliva, blood, or skin, to find genetic changes you were born with, and (2) testing on tumor tissue, which looks for possible changes arising only in the cancer and not the rest of the body. Depending on what type of cancer and at what stage, you may undergo one or both types of testing, so it is important to know what type of genetic testing you underwent.
Testing for inherited cancer risk can help guide some treatment options. For example, patients who have a known BRCA1/2 alteration may be aware of or have received PARP inhibitor therapy.
Testing on tumor tissue is different. For one thing, this testing often looks at hundreds more genes, which may change only in the cancer but not the rest of the body. For another thing, we may look for (1) overall changes across the tumor, such as tumor mutation burden, (2) in the actual gene sequences (DNA changes), or (3) in how genes are expressed (gene expression assays or RNA). When clinically indicated (meaning results of research have shown benefit to patients), testing for tumors can provide important information to guide treatment options that kill cancer cells in specific cancer types.