Abstract
PURPOSE: The aims of the study were to monitor circulating lymphocyte subset counts before and after therapy for nasopharyngeal carcinoma (NPC), and investigate their relationships with patient outcomes. PATIENTS AND METHODS: Subjects comprised patients with TNM stage I-IVA NPC who underwent radiotherapy. Peripheral venous blood samples were collected before and after treatment. Lymphocyte subset counts were analyzed by flow cytometry. Differences between post-treatment and baseline counts were calculated to determine Δ values. Patients were divided into high and low groups, based on median lymphocyte subset counts; propensity score matching was applied to balance groups. Progression-free survival (PFS) and overall survival (OS) were plotted using Kaplan-Meier curves and compared using a Log rank test. Relationships between lymphocyte subset counts and patient survival were subjected to Cox regression analysis. RESULTS: Patients with NPC (n=746) were enrolled from 2012-2022. Higher CD8(+) and total T cell baseline counts were associated with better 5-year PFS (73.7% vs 63.1%, P=0.002 and 73.8% vs 64.1%, P=0.005, respectively). Similarly, higher Δ values of CD4(+) and total T cells were associated with higher 5-year PFS (76.2% vs 63.5%, P=0.001; 74.3% vs 65.4%, P=0.010) and OS (89.8% vs 81.6%, P=0.005; 88.6% vs 82.5%, P=0.009). Multivariate Cox regression revealed that CD8(+) (hazard ratio (HR) 0.651, P=0.002) and total T (HR 0.600, P<0.001) cells were significantly associated with PFS. CD4(+) (HR 0.708, P=0.038) and total T (HR 0.639, P=0.031) cells were independent prognostic factors for OS. CONCLUSION: NPC patients with low total or CD8(+) T cell counts before treatment had worse prognosis; however, those with more significant decreases in total or CD4(+) T cells possibly had better outcomes. T cell counts can be reliable indicators to predict prognosis.