Immunotherapy induces durable responses in a subset of patients with
cancer. High TMB may be a response biomarker for PD-1/PD-L1 blockade in tumors
such as melanoma and non-small cell lung cancer (NSCLC). Our aim was to examine
the relationship between TMB and outcome in diverse cancers treated with various
immunotherapies. We reviewed data on 1,638 patients who had undergone
comprehensive genomic profiling and had TMB assessment. Immunotherapy-treated
patients (N = 151) were analyzed for response rate (RR),
progression-free and overall survival (PFS, OS). Higher TMB was independently
associated with better outcome parameters (multivariable analysis). The RR for
patients with high (≥ 20 mutations/mb) vs. low to intermediate TMB was
22/38 (58%) vs. 23/113 (20%) (P = 0.0001); median PFS,
12.8 vs. 3.3 months (P = <0.0001); median OS, not reached vs. 16.3
months (P = 0.0036). Results were similar when anti-PD-1/PD-L1
monotherapy was analyzed (N = 102 patients), with a linear correlation
between higher TMB and favorable outcome parameters; the median TMB for
responders vs. non-responders treated with anti-PD-1/PD-L1 monotherapy was 18.0
vs. 5.0 mutations/mb (P < 0.0001). Interestingly, anti-CTLA4/anti-PD-1/PD-L1
combinations vs. anti-PD-1/PD-L1 monotherapy was selected as a factor
independent of TMB for predicting better RR (77% vs. 21%) (P
= 0.004) and PFS (P = 0.024). Higher TMB predicts favorable
outcome to PD-1/PD-L1 blockade across diverse tumors. Benefit from dual
checkpoint blockade did not show a similarly strong dependence on TMB.
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