Selection of induction chemotherapy cycles for stage N3 nasopharyngeal carcinoma based on pre-treatment plasma EBV DNA

This study aimed to explore the selection of induction chemotherapy (IC) cycles for stage N3 nasopharyngeal carcinoma (NPC). We employed propensity score matching (PSM) to categorize patients into 3-cycle and 4-cycle IC groups (IC = 3 and IC = 4). The log-rank and chi-squared tests were used respectively to evaluate the differences in survival and acute toxicities. Survival outcomes including overall survival (OS), progression-free survival (PFS), distant metastasis-free survival (DMFS), and locoregional relapse-free survival (LRRFS) were evaluated among the two groups. After PSM, each group comprised 99 patients. The IC = 4 group exhibited markedly improved survival outcomes compared with the IC = 3 group. Multivariate analysis revealed that pre-EBV DNA was an independent risk factor affecting PFS and DMFS. For high-risk patients with pre-EBV DNA ≥ 7800 copies/ml, the IC = 4 group demonstrated greater survival compared to the IC = 3 group. Among low-risk patients with pre-EBV DNA < 7800 copies/ml, both groups showed comparable survival outcomes. In terms of acute adverse reactions, the IC = 4 group experienced higher incidences, particularly with grade 2-4 alanine transaminase elevation and thrombocytopenia. For stage N3 NPC, pre-EBV DNA could be a powerful predictor for guiding the selection of IC cycles. The IC = 4 regimen is probably more beneficial to high-risk patients due to superior survival, while for low-risk patients, the IC = 3 regimen may be sufficient.