Data presented at ESMO has demonstrated that a new blood test from Roche, co-developed with Foundation Medicine, can accurately measure the number of mutations within a tumour, which may help doctors to know which patients respond best to certain immunotherapies.

Tumour mutational burden (TMB) is a quantitative clinical marker that measures the number of mutations within a tumour genome. 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 a tumour biopsy. By using this blood-based testing approach, it may be possible to extend TMB testing to more patients, including those who are unable to undergo an invasive tumour biopsy, or where tissue is unavailable or of insufficient size to evaluate.

The TMB biomarker study being presented at ESMO was conducted using 794 plasma samples from trials of Roche’s own immunotherapy Tecentriq, and according to the company found that the biomarker could “measure TMB with a high degree of precision and accuracy” – independent of PD-L1 expression.

Immunotherapies, despite their efficacy, only work in a fraction of patients, which is particularly problematic given the high costs of these treatments. An accurate biomarker test is therefore much-desired by doctors and health services.

“Pursuing next generation biomarker development is a critical component of our cancer immunotherapy strategy,” said Sandra Horning, MD, Roche’s Chief Medical Officer and Head of Global Product Development. “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 toward personalisation of cancer therapy.”