Abstract
PURPOSE: To explore the influence of Epstein-Barr virus (EBV) DNA levels before and after induction chemotherapy (IC), tumor response to IC, and baseline factors on overall survival (OS) in patients with locally advanced nasopharyngeal carcinoma (LA-NPC). A nomogram was subsequently constructed to explore the individualized optimal cumulative cisplatin dose (CCD) in concurrent chemoradiotherapy (CCRT). METHODS: A total of 581 LA-NPC patients were included, randomly divided into training and validation cohorts in a 7:3 ratio. In the training cohort, a nomogram was subsequently established based on multivariate Cox regression analysis and then validated. Subsequently, patients were classified into different risk groups based on the nomogram, and the impact of different levels of CCD on survival outcomes was evaluated. RESULTS: EBV DNA levels after IC, tumor response to IC, age, and LDH were independent prognostic factors of OS. Schoenfeld residual analysis indicated overall satisfaction of the proportional hazards assumption for the Cox regression model. The C-index of the nomogram was 0.758 (95% CI: 0.695-0.821) for the training cohort and 0.701 (95% CI: 0.589-0.813) for the validation cohort. Calibration curves demonstrated good correlation between the nomogram and actual survival outcomes. DCA confirmed the clinical utility enhancement of the nomogram over the TNM staging system. For OS, patients in the medium/high-risk group with a CCD > 200 mg/m² had better outcomes than those with CCD ≤ 200 mg/m², although the difference was not statistically significant (p = 0.097). No significant difference was observed in local relapse-free survival (LRFS), distant metastasis-free survival (DMFS), and progression-free survival (PFS) across various levels of CCD in different risk subgroups (p > 0.05). CONCLUSION: The nomogram based on EBV DNA levels after IC, tumor response, LDH, and age effectively predicts OS in LA-NPC patients, aids in risk stratification, and may guide treatment decisions.