Detecting Chemosensitivity and Predicting Treatmemt Efficacy With CTCs in mNPC

Inclusion Criteria: * NPC patients with distant metastasis after 3 months of primary radiotherapy, and not suitable for local treatment * At least having one measurable metastatic lesion * All genders，range from 18～70 years old * ECOG score 0 \~ 1 * Expected survival time ≥ 3 months * White blood cell(WBC) count ≥ 3×109/L, neutrophile granulocyte(NE) count ≥ 1.5×109/L, hemoglobin(HGB) ≥ 90g/L, platelet(PLT) count ≥ 100×109/L * Alanine aminotransferase (ALT) or aspartate aminotransferase(AST) \< 2.5×upper limit of normal(ULN), bilirubin(BUN) or creatinine(CRE) \< 1.5×ULN, alanine aminotransferase (CCR) ≥ 60ml/min * Inform consent form Exclusion Criteria: * Have or are suffering from other malignant tumors; * Participating in other clinical trials; * Drug or alcohol addition; * Do not have full capacity for civil acts; * Mental disorder; * Pregnancy or lactation; * Severe complication, eg, uncontrolled hypertension.