Pan-cancer analysis of the effect of biopsy site on tumor mutational burden observations

Abstract

Plain language summary The total number of mutations, or changes, found within the DNA of cancer cells in a tumor sample is known as the tumor mutational burden (TMB). TMB scores have been proposed to be a marker of how well a tumor might respond to immunotherapy, a type of treatment that triggers the body’s immune system to target the cancer. Here, we look at whether TMB scores are dependent on the location in the body from which a tumor sample is taken, the biopsy site. We use over 100,000 specimens from 47 tissues for 12 different cancer types and test for associations between TMB scores and biopsy site. We find that the biopsy site has a strong impact on TMB score. These findings might impact on how clinicians interpret the results of genetic testing in patients and how they make decisions on treatment.