# TMB-high (tumour mutational burden >= 10 mutations per megabase)

Source: https://onco.cc/biomarkers/tmb-high/  
OnCo record `tmb-high` (Biomarker). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

TMB counts how many mutations a tumour carries per million DNA letters. Ten or more, measured by FoundationOne CDx, allows pembrolizumab for almost any solid tumour after other treatment has failed.

## Summary

Tumour mutational burden is the number of somatic non-synonymous (and, on some panels, synonymous) mutations per megabase of sequenced coding DNA, estimated from a large targeted panel and calibrated to whole-exome values. Pembrolizumab's US label (June 2020, KEYNOTE-158) covers unresectable or metastatic TMB-H solid tumours defined as >= 10 mutations per megabase by an FDA-authorised test, after prior treatment and with no satisfactory alternative; FoundationOne CDx is the listed companion diagnostic. Because panels differ in gene content and algorithms, a TMB of 10 on one assay is not the same as 10 on another; the label's limitation of use notes the benefit was not established in patients with central nervous system cancers. TMB is a genome-wide readout with no parent gene, so it sits under no target here.

## Fields

- Kind: Biomarker
- Last checked: 2026-09-23
- Also known as: TMB-H; TMB-high; TMB high; tumor mutational burden; tumour mutational burden; TMB >= 10 mut/Mb; TMB ≥10; TMB-H solid tumors; bTMB; blood TMB
- Tags: biomarker; genome-wide

## Sources

- KEYTRUDA prescribing information (DailyMed): https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=9333c79b-d487-4538-a9f0-71b91a02b287

## Connected records

- biomarkers: [ctDNA MRD positivity (molecular residual disease after curative treatment)](https://onco.cc/biomarkers/ctdna-mrd-positive/), [dMMR (mismatch repair deficiency by IHC)](https://onco.cc/biomarkers/dmmr-ihc/), [MSI-high (microsatellite instability by PCR or sequencing)](https://onco.cc/biomarkers/msi-high/)
- cancers: [Bladder & urothelial cancer](https://onco.cc/cancers/urothelial/), [Melanoma](https://onco.cc/cancers/melanoma/), [Metastatic cancer (cancer that has spread)](https://onco.cc/cancers/metastatic-cancer/), [Non-small-cell lung cancer](https://onco.cc/cancers/nsclc/)
- drugs: [FoundationOne CDx / Liquid CDx](https://onco.cc/drugs/foundationone-cdx/), [Pembrolizumab](https://onco.cc/drugs/pembrolizumab/)
- terms: [Neoantigen](https://onco.cc/terms/neoantigen/), [Next-generation sequencing (NGS)](https://onco.cc/terms/ngs/), [Tumour mutational burden (TMB)](https://onco.cc/terms/tmb/), [Tumour-agnostic (tissue-agnostic) approval](https://onco.cc/terms/tumour-agnostic/)

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