Anti-CTLA-4 antibody might be effective against non-small cell lung cancer with large tumors

Background: Immunotherapy using immune checkpoint inhibitors (ICIs) has revolutionized the treatment of advanced non-small cell lung cancer (NSCLC). Although several ICI options are available, the treatment regimen for NSCLC with large tumors (large NSCLC) is controversial and the efficacy of anti-CTLA4 antibody is unclear. We thus investigated potential biomarkers for CTLA-4 blockade. Methods We examined the correlation between tumor diameter and treatment duration in advanced NSCLC patients treated with anti-PD-1 antibody in our institution. In addition, we evaluated the ratio of tumor-infiltrating CD8 + T cells and regulatory T (Treg) cells in small and large NSCLC using immunohistochemical staining. Finally, we investigated the efficacy of treatment containing anti-CTLA4 antibody against large NSCLC. Results We found a negative correlation between tumor diameter and treatment duration in patients treated with anti-PD-1 antibody. Immunohistochemical staining revealed that Treg cell infiltration was significantly higher in large NSCLC tumors than in small tumors. We obtained a remarkable tumor reduction in patients with large NSCLC with an ICI regimen including anti-CTLA4 antibody. Conclusions Anti-PD-1 antibody might be less effective for large NSCLC due to the infiltration of Treg cells. Therefore, for large NSCLC, it might be appropriate to select a treatment with anti-CTLA4 antibody, which is expected to deplete Treg cells via antibody-dependent cellular cytotoxicity activity.