Background: Many studies have demonstrated several pharmacokinetic and pharmacogenetic factors may affect the efficacy and toxicity of 5-FU. These factors include system drug exposure (area under the concentration-time curve, AUC), thymidylate synthase (TS) and dihydropyrimidine dehydrogenase (DPD). This study is to investigate correlation of these factors and efficacy and toxicity of 5-FU and Cisplatin in NPC patients. Methods: 122 NPC patients with measurable lesions were enrolled and received Cisplatin (80mg/m², day1) and 5-FU (4g/m², civ120h) regimen. The blood samples were collected at steady state of 5-FU infusion. AUC of 5-FU measurement was performed using an immune-based assay (MyCare). The 5-FU AUC target range was identified by Received Operating Characteristic Curve (ROC), based on 5-FU related mucositis and treatment response. Tumor tissues were also collected for evaluation the expression of TS, DPD by using immunohistochemistry (IHC). Results: 108 patients were analyzed (5 not assessable, 6 withdraw and 3 invalid sample). AUC of 5FU values ranged from 15 to 103mg·h/L. The optimal target range of 5-FU AUC was 31-37 mg·h/L. 20.4% of the patients were within the target range, while 39.8% was below and 39.8% was above. Within or above target range patients had better object response rate than those below target (75.4% vs 55.8%, P=0.033), within or below target range patients had lower toxicity rate (grade3/4) than those above target (6.2% vs 67.4%, P<0.001). A nomogram model based on AUC, DPD and TS expression for predicting treatment response shown that, all as independent variables, within the target AUC range, high-DPD or low-TS tumor had better response rate. Conclusions: The combination of pharmacokinetic and pharmacogenetic approach may be an innovative strategy for optimizing chemotherapy in patients with advanced NPC. These findings deserve confirmation in additional prospective studies.