Changes and significance of immune-related indicators in patients with recurrent/metastatic nasopharyngeal carcinoma before and after PD-1 inhibitor combined with GP regimen chemotherapy.

e18036 Background: To investigate the dynamic changes of peripheral blood immune-related indicators and their association with therapeutic efficacy in patients with recurrent/metastatic nasopharyngeal carcinoma (NPC) treated with PD-1 inhibitors combined with the GP regimen. Methods: A retrospective analysis was conducted on 46 patients with recurrent/metastatic NPC. All patients received at least one PD-1 antibody inhibitor (camrelizumab/toripalimab/sintilimab/tislelizumab) combined with GP (gemcitabine + cisplatin) chemotherapy. Peripheral blood samples were collected at baseline and after three treatment cycles to measure immune-related indicators, including PD-1, CTLA-4, and Treg cells. The expression differences of these indicators at baseline between the objective response group (PR+CR) and the poor-response group (SD+PD), as well as their dynamic percentage changes during treatment, were compared. Univariate and multivariate logistic regression analyses were further performed to determine whether PD-1, CTLA-4, Treg, CD4+/CD8+ ratio, CD3+, CD4+, CD16+, PDC, and MDC were independent factors influencing treatment efficacy. Results: Baseline peripheral blood PD-1 expression was significantly lower in the objective response group (PR+CR) compared to the poor-response group (SD+PD) (p0.05), while trends of increase were noted for CTLA-4, CD3+, MDC, and PDC (p>0.05). After treatment, levels of PD-1 and CD16+ decreased significantly compared to baseline (p0.05). Multivariate logistic regression analysis indicated that PD-1 was an independent factor influencing treatment efficacy in patients with recurrent/metastatic NPC (p<0.05). Conclusions: PD-1 inhibitor combined with GP regimen chemotherapy demonstrates favorable efficacy in recurrent/metastatic NPC. Low baseline PD-1 expression may be associated with better therapeutic outcomes. The significant post-treatment decrease in PD-1 and CD16+ expression may suggest immune cell activation and migration to tumor sites following treatment.