Some cancers generate the seeds of their own destruction. Certain random mutations that accumulate in rapidly dividing tumor cells can spur the immune system to attack the cancer. Researchers are now learning that the extent of such mutations can predict whether a cancer will respond to new, powerful, immune-based therapies. A recently unveiled blood test for this so-called tumor mutational burden (TMB) could help make it a practical tool for guiding cancer treatment.
Cancer researchers can already gauge TMB by sequencing a panel of select genes in biopsied tissue, an approach that recently demonstrated strong predictive power in a large lung cancer trial. Some cancer physicians now use tissue TMB tests in select cases. But the less-invasive blood test, which analyzes tumor DNA shed into a person’s circulation, could reveal TMB in the many patients where tissue testing doesn’t work.
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Tests that can predict whether immunotherapy will work in a patient are badly needed, especially for so-called checkpoint inhibitors, which release a brake on immune cells and enable them to attack tumors. Since the Food and Drug Administration (FDA) in 2014 approved the first antibody drug targeting the “checkpoint” protein called PD-1, these drugs have transformed cancer care.
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In April, FDA designated the blood TMB test a “breakthrough device” that merits a priority review. But whether from blood or biopsies, it’s not clear TMB will give doctors and patients the outcomes or certainty they crave.
Read full, original post: Mutation-counting blood test could predict if cutting-edge immunotherapies can beat a cancer
