The prospective observational clinical study will recruit 50 metastatic nasopharyngeal carcinoma (mNPC) patients, detecting patient's chemosensitivity with the circulating tumor cells (CTCs) from peripheral blood and prdicting patient's treatment efficacy with CTCs dynamic change.

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.

NPC patients with distant metastasis after 3 months of primary radiotherapy