PD-L1 and tumor mutation burden (TMB) are the most widely used immunotherapy biomarkers to identify populations who would attain clinical benefit, with the higher values predicting the better therapeutic efficacy. This review will address the predictive values and unresolved challenges of these two biomarkers.
PD-1 and PD-L1 inhibitors have induced durable and effective responses in patients with advanced non-small cell lung cancer (NSCLC), confirmed by multiple clinical trials and real-world studies. Different clinical trials, involving both PD-1/PD-L1 inhibitors alone and combination regimens, adopted either PD-L1 or TMB to stratify the patients, although the predictive capabilities of these two biomarkers are different. In the first-line setting, PD-L1 of 50% or more as a cut-off value can help select candidates for pembrolizumab or atezolizumab monotherapy; however, these two biomarkers poorly predict the efficacy of immunotherapy combination regimens as first-line treatments. In the second-line setting, although patients can benefit from nivolumab regardless of PD-L1 expression, both PD-L1 and blood TMB (tTMB) can be used as biomarkers to find patients suitable for atezolizumab. Expect for inaccurate predictiveness, there are many unresolved problems with regard to the two biomarkers such as the lack of standard detection methods, and their susceptibilities to other dynamic changes.
The predictive values of TMB and PD-L1 were low in most circumstances; however, PD-L1 expression greater than≥50% can help select appropriate patients for pembrolizumab and atezolizumab, respectively, as first-line monotherapies; and higher PD-L1 or TMB was associated with greater efficacy for atezolizumab as a second-line monotherapy.

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