Mutation load and an effector T-cell gene signature may distinguish immunologically distinct and clinically relevant...

Identifying follicular lymphoma (FL) patients with preexisting antitumor immunity will inform precision medicine strategies for novel cancer immunotherapies. Using clinical and genomic data from 249 FL patients, we determined the clinical impact of mutation load and an effector T-cell (T_eff) gene signature as proxies for the likelihood of a functional immune response. The FL mutation load estimate varied between 0 and 33 mutations per Mb (median, 6.6), and 92% of FL patients with a high mutation load had high T_eff gene expression (P = .001). The mutation load was associated with a benefit from rituximab maintenance: FL patients with low mutation loads experienced a profound benefit from rituximab maintenance (hazard ratio [HR], 0.29; 95% confidence interval [CI], 0.15-0.54; P < .001). The T_eff gene signature was prognostic as a continuous predictor (P = .008), and was used to separate FL patients into 2 groups, an "inflamed" subset (T_eff-high; n = 74) and an "uninflamed" subset (T_eff-low; n = 75), with longer progression-free survival (PFS) in the inflamed FL subset (PFS HR, 0.39; 95% CI, 0.21-0.70; P = .002). Furthermore, the subset of inflamed FL tumors demonstrated high expression of other T-cell signatures and counterregulatory genes, which also correlate with PFS. Mutation load and T_eff gene expression may help identify immunologically distinct lymphoma subsets relevant for modern immunotherapies.