Abstract
Purpose: To investigate the inter-correlation of tumor spread, volume and quantitative plasma Epstein-Barr virus DNA level (pEBV DNA), and to further assess the prognostic efficacy of a novel risk stratification combining anatomic, volumetric and biological features in nasopharyngeal carcinoma (NPC). Methods and Materials: One hundred and twelve patients with non-metastatic NPC were prospectively enrolled. Correlation of pEBV DNA with tumor invasiveness, lymph node (LN) metastasis, tumor volume and classification was tested by univariate and multivariate analyses. 5-year distant metastasis free survival (DMFS) was evaluated using Kaplan-Meier method and Cox proportional hazards model. Results: Tumor volume, TNM stage and pEBV DNA were strongly inter-correlated to each other. Nodal volume, skull base invasion and LN metastasis to supraclavicular fossa were determined to be independent predictors for pEBV DNA level. To exclude collinearity, a risk stratification based on combination of EBV DNA, nodal volume and anatomic features was established, offering significant distinguishing ability in 5-year DMFS. Further multivariate Cox regression analysis found the novel stratification to be independent predictor of DMFS. Conclusions: Both anatomic spread and tumor volume contribute to pEBV DNA level, leading to strong inter-correlation between NPC stage, volume and EBV DNA. The proposed risk stratification combining anatomic, volumetric and biological features showed potential in refining DMFS prediction.