A biomarker is something in the body that can be measured to give useful information. For cancer, biomarkers can be used to guide whether a certain therapy is a good choice for a particular individual.
Tests, called molecular tests or biomarker tests can tell how much of the PD-L1 protein is in cancer. In general, if there is a lot of PD-L1, the cancer is more likely to respond to a PD-1 or PD-L1 inhibitor (such as Opdivo, Keytruda or Tecentriq).
Unlike molecular testing for targeted therapies, testing for immunotherapies is not black and white. A cancer can be PD-L1 “high” and not respond to the drug. It can also “low” and still respond. This is just less likely.
Molecular testing can also show if there are a lot of gene changes (mutations) in the cancer. Some immunotherapies seem to work better if your cancer has a large number of changes. Gene changes may be caused by exposure to environmental agents like cigarette smoke. Gene changes can also happen when genes do not repair themselves properly. Some cancers have problems with genes repairing themselves called microsatellite instability (MSI) or deficient mismatch repair (MMR). If you have these biomarkers, your cancer is also more likely to respond to PD-1/PD-L1 inhibitors.
Research is ongoing to find new and better biomarkers to guide your treatment decisions. For example, studies are currently looking at a measure of the number of gene changes in the cancer, called tumor mutational burden (TMB). Early research data shows that immunotherapies may work better in cancers with high TMB. This may guide treatment decisions soon.
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