Maintenance Therapy With Toripalimab Combined With Capecitabine/Placebo for Recurrent and Metastatic Nasopharyngeal Carcinoma

Inclusion Criteria: 1. The age at the time of diagnosis is 18-75 years old, regardless of gender; 2. Histologically confirmed nasopharyngeal carcinoma; 3. Confirm the presence of distant metastasis in advanced nasopharyngeal carcinoma patients or recurrent nasopharyngeal carcinoma patients who cannot receive local treatment. ; 4. After receiving standard treatment for 4-6 cycles, the disease is control; 5. ECOG score 0-1; 6. Expected survival time of at least 12 weeks; 7. Patients who have not received systemic chemotherapy within 6 months prior to diagnosis ; 8. According to RECIST 1.1 standard, at least 1 measurable lesion; 9. Enough organ function; 10. Sign an informed consent form; 11. Female participants with fertility and male participants with fertility partners must agree to use reliable contraceptive measures within 6 months after screening and the last treatment. Exclusion Criteria: 1. Patients who are known to be intolerant to capecitabine or allergic to any therapeutic drug, or who are participating in clinical studies of other new drugs; 2. Diseases that may interfere with oral medication treatment, including but not limited to swallowing difficulties, chronic diarrhea, or intestinal obstruction; 3. Previous or current history of other tumors, excluding cured cervical carcinoma in situ, skin basal cell carcinoma, and thyroid papillary carcinoma; 4. Sever heart disease; 5. Central nervous system metastasis with clinical symptoms; 6. Serious infections ; 7. Within 4 weeks of signing the informed consent form, receive systemic hormone or other immunosuppressive therapy with an equivalent dose greater than 10mg prednisone per day. Subjects with a systemic hormone dose ≤ 10mg prednisone per day or inhaled/topical corticosteroids can be enrolled in the study; 8. Patients with active chronic hepatitis B or active hepatitis C. 9. A history of interstitial pneumonia or other autoimmune diseases. 10. HIV infection; 11. Individuals with significant organ dysfunction or uncontrollable comorbidities, including but not limited to uncontrollable hypertension, decompensated liver cirrhosis, active peptic ulcer, or hemorrhagic disease; 12. Less than 6 weeks after major organ surgery; 13. Pregnant or breast feeding; 14. Patients with mental illness, those with a history of alcohol or drug abuse, or those who are unable to obtain informed consent; 15. Other researchers have determined that it is not suitable to participate in this trial. 16. Those who refuse or are unable to sign the informed consent form.