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Introduction: Novel predictive biomarkers are needed to optimize immunotherapy-based treatment response in non-small cell lung carcinoma (NSCLC). T cell modulatory features may limit the ability of T cells to mount effective anti-tumor responses and could predict immune fitness and responsiveness to therapy. We investigated the prognostic and predictive value of CD8+ T cells with an exhausted phenotype, specifically those co-expressing Programmed Death 1 (PD-1) and T cell factor 1 (TCF-1), in peripheral blood of NSCLC patients before any systemic treatment.

Methods: Two patient cohorts were analyzed: a) 32 patients with early and locally advanced disease (stage I–IIIA; cohort A) who did not receive immunotherapy, and b) 47 patients with advanced disease (stage IIIB-IV) who received chemo-immunotherapy. Multicolor flow cytometry was used to assess CD8+ T cell subpopulations co-expressing PD-1 and TCF-1.

Results: PD-1+TCF1+ progenitor (early) exhausted T cells were found at high frequencies in all NSCLC patients compared with healthy donors, regardless of tumor stage. In cohort A, patients with high levels of CD3+CD8+PD-1+TCF1+ T cells had significantly improved DFS (p= 0.038), while those with high CD3+CD8+PD-1+TCF1− T cells had significantly worse DFS (p= 0.028). In cohort B, high levels of CD3+CD8+PD-1+TCF1+ T cells were associated with shorter PFS (p= 0.027). No association with OS was observed in cohort A. Conversely, in cohort B, high CD3+CD8+PD-1+TCF1+ T cell levels correlated with shorter OS (p= 0.045), while high CD3+CD8+PD-1+TCF1− T cell levels correlated with longer OS (p= 0.010).

Conclusion: Therefore, here we show that circulating PD-1⁺TCF1+ T cells correlated differentially with treatment outcome in early and late NSCLC stage patients.