Abstract
Foundation Medicine has added the first fully integrated and validated assessments of tumor mutational burden (TMB) and microsatellite instability (MSI) to its FoundationOne and FoundatationOne Heme products, markers that can help oncologists gain deeper insight into potential individual patient responses to immunotherapy treatments for cancer. The additional markers expand the company's products geared toward cancer immunotherapy, which already include tests for PD-1 and PD-L1 protein expression.
“Cancer immunotherapies are at the forefront of cancer treatment, and new, quantitative approaches are needed to predict clinical responses to this important, but also expensive, class of therapies,” said Vincent Miller, M.D., chief medical officer of Foundation Medicine. “Prior to our ability to measure TMB and MSI with FoundationOne, these biomarkers could only be detected separately, either through tests such as immunohistochemistry, polymerase chain reaction (PCR) or whole exome sequencing. Integrating this capability to measure TMB and MSI with one tissue sample, and reported in one test, represents an important advance in clinical care.”
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TMB is described as the total number of DNA mutations per megabase in a tumor sequence. The use of TMB scoring has been gaining favor as a predictor of the likelihood of patients to respond to cancer immunotherapy treatments. Three separate abstracts presented at the American Society of Clinical Oncology (ASCO) annual meeting earlier this year focused on TMB as a possible predictor of immunotherapy response in non-small cell lung cancer, melanoma, and urothelial carcinoma, with each showing correlation between measured TMB and immunotherapy treatments.
This phenomenon has been validated across a wide range of tumor types, including advanced bladder cancer, lung cancer, breast cancer, colorectal cancer, advanced head and neck cancer and melanoma. Some tumors develop high TMB as a result of defective mismatch repair of DNA, a condition in which the length of certain DNA areas becomes more widely varied than normal. This condition, which is referred to as MSI-high and MSI-high tumors, almost always has a high TMB.
“The ability to accurately measure multiple biomarkers simultaneously, including TMB and MSI, is an important advance for the field of cancer immunotherapy,” said Thomas George, M.D., GI oncology program director, University of Florida.