Blood-based tumor mutational burden (bTMB) helped to predict which patients with non-small cell lung cancer (NSCLC) would numerically benefit from atezolizumab monotherapy, according to results of the B-F1RST trial presented at the European Society for Medical Oncology (ESMO) Congress 2019.

A primary analysis of the study done with 6 months or more of follow-up showed that patients with bTMB high (score of ≥16) had a higher overall response rate compared with bTMB low (28.6% vs 4.4%, respectively). 

The study was conducted in 152 patients with untreated stage IIIB to stage IVB NSCLC. Patients received atezolizumab monotherapy until disease progression, intolerance, or loss of benefit. 

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This final analysis of the data was done with 18 months or more of follow-up. The overall response rate was 17%, with a median progression-free survival of 4.1 months and a median overall survival of 14.8 months. 

Median progression-free survival was numerically higher among patients with bTMB-high compared with mTMB-low (5.0 months vs 3.5 months, respectively), as was the median overall survival (23.9 vs 13.4 months, respectively). 

The researchers also evaluated serum C-reactive protein (CRP) as a surrogate biomarker. Patients with a CRP at C3D1 to CRP at screening ratio of less than 0.5 had a median progression-free survival of 14.1 months compared with 4.6 months with a ratio of 0.5 or higher (hazard ratio [HR], 0.43; 90% CI, 0.24-0.77). 

Approximately 1 in 5 patients (18%) had adverse events that led to treatment discontinuation. Grade 3/4 adverse events occurred in 20% of patients. 

According to the researchers, “this final analysis confirmed that patients with bTMB ≥16 had numerical benefit for progression-free and overall survival.”

Disclosure: The study was funded by F. Hoffman-La Roche, Ltd. For a full list of author disclosures, please refer to the original abstract.


Socinski M, Velcheti V, Mekhail T, et al. Final efficacy results from B-F1RST, a prospective phase II trial evaluating blood-based tumour mutation burden (bTMB) as a predictive biomarker for atezolizumab (atezo) in 1L non-small cell lung cancer (NSCLC). Presented at:  LBA83. Presented at: European Society for Medical Oncology (ESMO) Congress 2019; September 27-October 1, 2019: Barcelona, Spain.