Tumor Mutational Burden (TMB)
TMB is a Pan-Tumor Biomarker for IO Response
TMB by Whole Exome Sequencing measures the total number of non-synonymous, somatic mutations identified per megabase
(Mb) of the genome coding area of DNA (a megabase is 1,000,000 DNA basepairs).
- Non-synonymous mutations are changes in DNA that result in amino acid changes in the protein.1,2
- The new protein changes result in new shapes (neo-antigens) that are considered to be foreign to the immune system.1,3
- Immune checkpoint inhibitors are able to stimulate and allow the immune system to detect these neo-antigens and destroy the tumor.2
- Germline (inherited) mutations are not included in TMB because the immune system has a higher likelihood of recognizing these alterations as normal.4
TMB has emerged as an important biomarker when considering immunotherapy in solid tumors. This is highlighted by the recent U.S. FDA accelerated approval of pembrolizumab (KEYTRUDA®) for the treatment of adult and pediatric patients with unresectable or metastatic tumor mutational burden-high (TMB-H) [≥10 mutations/megabase (mut/Mb)] solid tumors that have progressed following prior treatment and who have no satisfactory alternative treatment options. This approval is based on the results of the KEYNOTE-158 trial, which achieved an overall response rate of 29% (95% CI: 21, 39), with a 4% complete response rate and 25% partial response rate.5
TMB is included with all Caris Molecular Intelligence orders (MI Profile™ and MI Tumor Seek™) and is performed using Whole Exome Sequencing
Caris Molecular Intelligence TMB-H Cutoff Aligned Across All Solid Tumors
Genomic profiling with Caris Molecular Intelligence can help you make more informed therapy decisions when
considering immune checkpoint inhibitors.
In addition, Caris has been working in collaboration with the Friends of Cancer Research TMB Harmonization Project to systematically characterize and standardize TMB testing and reporting to a common industry standard.6 Based on this collective work and exciting KEYNOTE-158 result and drug approval, Caris has updated the TMB high/low threshold to reflect greater than or equal to 10 mutations per megabase across all solid tumors, aligning the testing results to pembrolizumab for TMB-H cases.5
1. Snyder A. N Engl J Med. 2014; 371:2189-2199. doi:10.1056/ NEJMoa1406498
2. Le DT. N Engl J Med. 2015;372:2509-2520. doi:10.1056/NEJMoa1500596
3. Rosenberg JE. The Lancet. 2016; 387(10031):1909-1920. doi:10.1016/S0140-6736(16)00561-4.
4. Stewart TJ. Oncogene. 2008;27:5894-5903. doi:10.1038/onc.2008.268
5. U.S. Food and Drug Administration. (2020, June 16). FDA approves pembrolizumab for adults and children with TMB-H solid tumors [Press release].
6. Stenzinger, A, Allen, JD, Maas, J, et al. Tumor mutational burden standardization initiatives: Recommendations for consistent tumor mutational burden assessment in clinical samples to guide immunotherapy treatment decisions. Genes Chromosomes Cancer. 2019; 58: 578– 588. https://doi.org/10.1002/gcc.22733