Optimal induction chemotherapy courses in nasopharyngeal carcinoma in the IMRT era: A recursive partitioning risk stratification analysis based on EBV DNA and AJCC staging.

OBJECTIVES: To compare the prognosis and adverse effects in patients treated with different courses of induction chemotherapy (IC) in the intensity-modulated radiotherapy (IMRT) era. MATERIALS AND METHODS: 4404 patients diagnosed from 2008 to 2021 were enrolled. Our primary endpoint was progression-free survival (PFS). The recursive partitioning analysis (RPA) was applied to derive a risk stratification system. The inverse probability of treatment weighting (IPTW) was used to reduce or eliminate the effect of unbalanced characteristics between subgroups. Kaplan-Meier survival curves were used to assess the survival rates and cox analysis was applied to evaluate the relationship between variables and endpoints. RESULTS: The RPA-based risk stratification comprising pretreatment EBV DNA (pIC-EBV DNA) level and the AJCC staging system identified 3 different risk groups, and there was no statistically significant difference in patients receiving different courses of IC in PFS in the entire cohort. The IPTW-adjusted analyses showed that there was no significant difference in patients receiving different courses of IC in the entire group and different risk groups. The multivariate Cox analyses also revealed that the number of courses in IC was not associated with PFS in the entire cohort (3 courses vs 2 courses: HR, 0.95, 95 %CI: 0.77-1.17; 4-6 courses vs 2 courses: HR, 0.83, 95 %CI: 0.59-1.16). CONCLUSION: Two courses may be the optimal induction chemotherapy courses for locoregionally advanced NPC patients in the IMRT era. Additional courses of IC should be applied with caution, since patients may not benefit from more courses but instead suffer more adverse events.