Blood Test Predicts Immunotherapy Efficacy
By Labmedica International staff writers
Posted on 20 Sep 2017
Image: The Tumor Mutation Burden test detects cell free tumor DNA in the blood and allows for stratification of patients not eligible to have a tumor biopsy (Photo courtesy of the US National Cancer Institute).
A test developed with the US-based genetic testing specialist could be significant because, although potent, it is difficult to predict which patients will respond to immunotherapies, which are setting new care standards in some types of tumors.
This and the tough side-effects associated with immunotherapies have led to some unpleasant surprises where trials have produced unexpected failures, and but scientist hope that testing Tumor Mutation Burden (TMB) will more accurately predict where immunotherapies will succeed.
TMB is a clinical marker that measures the number of mutations within a tumor genome, and the new data show for the first time that a blood-based test can measure this with a high degree of precision and accuracy. TMB has been found to be an indicator of likelihood of progression-free survival (PFS) benefit from immunotherapies when used alone (monotherapy) in patients with non-small cell lung cancer (NSCLC).
Until now TMB could only be measured using an invasive tumor biopsy, and a blood test could extend tests to patients unable to undergo these procedures, or where tissue is unavailable or of insufficient size to evaluate. The blood TMB (bTMB) biomarker study was conducted using 794 plasma samples from the pivotal phase 2 POPLAR and phase 3 OAK Tecentriq studies. The purpose of the analysis was to collect initial, retrospective evidence of an association between bTMB and Tecentriq activity. These early data will inform ongoing and future prospective studies to better understand the role of both TMB and bTMB as it relates to treatment with cancer immunotherapy.
The blood test for TMB was developed by Roche (Basel, Switzerland) and Foundation Medicine (Cambridge, MA, USA) and has shown it can accurately measure the number of mutations within a tumor, potentially helping doctors predict which patients may respond best to some immunotherapies. Sandra Horning, MD, Roche's chief medical officer, said, “Biomarkers will not only improve our understanding of immune biology but will ultimately help match our therapies and combinations to the people most likely to benefit. This blood-based TMB assay is one example of how we and our partners are advancing the science towards personalization of cancer therapy.” The study was presented at the European Society of Medical Oncology Congress held September 8-12, 2017, in Madrid, Spain.