Test every colorectal tumor for mismatch repair and gene changes
Results can reveal Lynch syndrome and decide immunotherapy and targeted drugs.
What studies found
The American Cancer Society says all colorectal cancers should now be tested for mismatch-repair deficiency (MMR) or microsatellite instability (MSI). A deficient result leads to genetic testing for Lynch syndrome and opens immunotherapy options proven in randomized trials. For cancer that has spread, gene changes such as BRAF V600E point to matched drugs, and the National Cancer Institute notes that biomarker tests help predict response to targeted therapy.
The catch
Testing guides treatment; it doesn't change outcomes by itself.
What to do
Ask whether your tumor was tested for MMR or MSI and, if the cancer has spread, for other gene changes.
Sources
Rung 5 of 5, Established: Large randomized trials or overwhelming, consistent human evidence; reflected in major guidelines. How we score
Step by step
For the whole picture, from prevention and screening to treatment and life after, see the colorectal cancer page.
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