A blood test found rare repair gene changes in brain tumors
Original title: Beyond variant detection: Mismatch repair gene alterations in plasma cell-free DNA from 1,226 glioma samples, and plasma-confirmed functional deficiency in an unbiopsied pontine glioma.
How far along is this research?
- Lab cells
- Animals
- Review
- Tested in people
This was tested in people. That is the most reliable kind of research we share.
This looked back at tests already done in people, plus one child's case, not a new trial.
The short version
A blood test may spot a rare gene change when a tumor cannot be safely biopsied.
What was studied. Researchers checked blood tests from 1,226 glioma: A tumor that starts in the glial cells, the support cells of the brain and spinal cord. Gliomas are given a grade from 1 to 4 describing how the tumor is expected to behave. See the glossary samples and compared them with 5,369 tumor tissue samples. They also report one child with a brain stem tumor that was never biopsied.
What they found. In that child's blood, the test found a change in a gene called MSH6. The child took a drug called pembrolizumab for 21 doses, scans stayed stable, and the tumor grew again at about 19 months. In the larger group, 680 of 1,226 blood samples had at least one gene change, with MSH6 changed in 8, MSH2 and MLH1 in 6 each, and PMS2 in 2.
What this means, and what it doesn't
What it could mean: When a tumor cannot be biopsied safely, a blood test may still give useful clues. A positive result could point to a small group of patients who might try a certain type of drug. It is fair to ask your care team whether blood-based gene testing fits your case.
What it doesn't mean: This does not mean a blood test can replace testing a piece of the tumor. The authors say blood testing adds to tissue testing, it does not take its place. A normal blood result does not rule the gene change out. Most of this work looked back at records already collected, and the child's story is just one case. It is not a cure, and it is not proof that any drug works for this.
Source: PubMed, September 23, 2026 · Read the original
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