Foundation Medicine’s novel, investigational bTMB assay has already demonstrated clinical validity, and may be able to address these challenges. The recent published article below is showing that bTMB assay could help predict response to the anti-PD-L1 immunotherapy atezolizumab in patients with previously treated non-small cell lung cancer (NSCLC).
The results also show that bTMB may be an independent predictor of clinical benefit, regardless of PD-L1 biomarker expression as assessed by immunohistochemistry for NSCLC patients who also had an available tissue biopsy.

https://www.nature.com/articles/s41591-018-0134-3