PFLL Combined With PD-1 Antibody With or Without FMT for Oligometastatic NPC,a Phase III ,Open, Randomized Clinical Trial.

Inclusion Criteria:

1. 18-60 years old;

2. Pathological diagnosis of nasopharyngeal carcinoma;

3. Patients diagnosed with oligometastatic nasopharyngeal carcinoma who meet stage IVbas defined by the International Union against Cancer and the American JointCommittee on Cancer (UICC/AJCC) staging System (8th edition) (Oligometastatic as ≤3organs and ≤5 sites of metastasis);

4. Patients with metastatic nasopharyngeal carcinoma who had not previously receivedsystematic chemotherapy for the disease in this study, except neoadjuvantchemotherapy, concurrent chemoradiotherapy or adjuvant chemotherapy received 6months before the first administration;

5. Karnofsky's functional status score should be at least 70 points (if the functionalstatus score is decreased due to tumor, it should be appropriately relaxed after theresearchers' judgment, and the minimum score should be no less than 50 points, asshown in Annex I);

6. According to the RECIST1.1 evaluation criteria, there should be at least 1measurable lesion, and the measurable lesion should not have received localtreatment such as radiotherapy;

7. Expected survival ≥3 months;

8. A tolenrant organs.

Exclusion Criteria:

1. allergy to 5-FU, gemcitabine, cisplatin, other monoclonal antibodies, or anycomponent of triplimab

2. Prior treatment with PD-1 receptor or its ligand PD-L1 or cytotoxic Tlymphocyte-associated protein 4 (CTLA4) receptor;

3. Had major surgery other than diagnosis of nasopharyngeal cancer within 28 days priorto randomization or was expected to require major surgery during the study period;

4. Patients with severe damage of intestinal barrier such as sepsis, active massivebleeding of digestive tract and perforation due to various reasons;

5. Currently diagnosed with fulminant colitis or toxic megacolon;

6. Enteral nutrition patients who cannot tolerate 50% of heat calorie requirements dueto severe diarrhea, significant fibrous intestinal stenosis, severe gastrointestinalbleeding, high-flow intestinal fistula, etc.;

7. patients with any active autoimmune disease or a history of autoimmune diseases.