Characterization of the immune cell profile in metastatic nasopharyngeal carcinoma treated with chemotherapy and immune checkpoint inhibitors.

Nasopharyngeal carcinoma (NPC) is an Epstein-Barr virus (EBV)-associated cancer, and immune checkpoint inhibitors (ICIs) have shown efficacy in its treatment. The combination of chemotherapy and ICIs represents a new trend in the standard care for metastatic NPC. In this study, we aim to clarify the immune cell profile and related prognostic factors in the ICI-based treatment of metastatic NPC. Programmed cell death ligand 1 (PD-L1) expression was measured in 81 metastatic tissue samples that had not received prior ICI treatment. The combined positive score (CPS) was positive in 58.0% of the samples, with a statistically significant correlation to median overall survival (OS) (CPS ≥ 1 vs. CPS < 1: 28 vs. 16 months, P = 0.004). For the combination treatment of metastatic NPC, 62 patients were enrolled in a retrospective analysis, yielding a median OS of 39.3 months. The objective response rate for this combination therapy was 71%, with a complete response rate of 45.2%. With a cutoff value of 4.8 for the pre-treated neutrophil-lymphocyte ratio (NLR) in peripheral blood (PB), the difference in median OS was statistically significant (P = 0.021). Thirty-seven patients received local treatment following the combination therapy of ICIs and chemotherapy, which provided additional survival benefits. Most hyper-responders exhibited a prolonged low NLR (< 3), a high total lymphocyte count, and an undetectable or stable EBV DNA load in PB during treatment. Peripheral blood mononuclear cells (PBMCs) from most patients receiving the combination treatment were rich in PD-1+CD8+ lymphocytes, which showed high expression of both IFN-γ and Granzyme B, demonstrating the ability to kill the EBV-positive NPC cell line and xenografts in vitro and in vivo. Responders also displayed increased levels of CD4+CD45RA-CCR7-CD28+CD57- cells (effector memory cell subset) in peripheral blood. These results indicate that in the context of combined chemotherapy and ICIs, high PD-L1 expression in pre-treated metastatic tumor tissue, a low NLR before treatment, a decrease in NLR after treatment, and local treatment can provide significant benefits for patients with metastatic NPC.