PD-1 Inhibitor Plus Chemotherapy Followed by Immediate Versus Salvage Locoregional Radiotherapy in De Novo Metastatic NPC

Nasopharyngeal carcinoma (NPC) is highly prevalent in Southern China, with approximately 15% of patients presenting with distant metastases at diagnosis. A PD-1 inhibitor combined with gemcitabine and cisplatin (GP) has become the standard first-line therapy for metastatic NPC. However, the survival benefit of adding immediate locoregional radiotherapy to PD-1 inhibitor plus GP in de novo metastatic NPC remains uncertain. This phase III randomized trial is designed to compare immediate versus salvage locoregional radiotherapy following PD-1 inhibitor plus GP in de novo metastatic NPC, with the objective of determining whether salvage radiotherapy is non-inferior to immediate radiotherapy while offering reduced toxicity.

Inclusion criteria

• Age 18-70 years, any gender.
• Histologically confirmed differentiated non-keratinizing carcinoma or undifferentiated non-keratinizing carcinoma by tissue biopsy, with radiologically detectable metastatic lesions. Pathological confirmation of metastatic lesions is recommended but not mandatory.
• ECOG performance status 0-1.
• Stage IV NPC according to the 9th edition of the UICC/AJCC staging system.
• No prior anti-tumor treatment for NPC (radiotherapy, chemotherapy, surgery, etc.).
• Expected survival ≥ 3 months.
• At least one measurable lesion per RECIST v1.1.
• Achieved complete response (CR) or partial response (PR) after 4-6 cycles of chemotherapy plus PD-1 inhibitor therapy.
• Adequate organ function within 14 days before first dose, defined as:

Hematology：Hemoglobin ≥ 90 g/L，ANC ≥ 1.5 × 10⁹/L，Platelet count ≥ 100 × 10⁹/L Renal Function：Creatinine ≤ 1.5 × ULN, or creatinine clearance (CrCl) / eGFR ≥ 60 mL/min Liver Function：Total bilirubin ≤ 1.5 × ULN，AST and ALT ≤ 2.5 × ULN, or ≤ 5 × ULN in the presence of liver metastases

• INR or PT ≤ 1.5 × ULN, unless on therapeutic anticoagulation and values within therapeutic range，aPTT ≤ 1.5 × ULN, unless on therapeutic anticoagulation and values within therapeutic range

Exclusion criteria

• Prior anti-tumor therapy for nasopharyngeal carcinoma, including radiotherapy, chemotherapy, surgery, or immunotherapy.
• Prior treatment with PD-1/PD-L1 or CTLA-4 inhibitors.
• Presence of uncontrolled or symptomatic central nervous system (CNS) metastases.
• History of other malignancies within the past 5 years, except adequately treated basal cell carcinoma, squamous cell skin cancer, or in-situ cervical cancer.
• Active autoimmune disease or history of autoimmune disease requiring systemic treatment (e.g., corticosteroids, immunosuppressants) within the past 2 years, except for stable hypothyroidism, type 1 diabetes mellitus, or resolved childhood asthma/atopy.
• Known history of active pulmonary tuberculosis (TB). Suspected active TB must be excluded by chest X-ray, sputum examination, and assessment of clinical signs and symptoms.
• Hepatitis B: HBsAg positive with peripheral blood HBV DNA ≥ 1000 copies/mL
• Hepatitis C: HCV antibody positive, eligible only if HCV RNA is negative
• HIV infection
• Clinically significant cardiovascular disease (e.g., uncontrolled hypertension, unstable angina, myocardial infarction within 6 months, congestive heart failure ≥ NYHA class II, or serious arrhythmia).
• Interstitial lung disease, non-infectious pneumonitis, or history of ≥ grade 2 pneumonitis.
• Major surgery within 4 weeks before enrollment, or unhealed surgical wound.
• Pregnant or breastfeeding women, or those planning pregnancy during the study period.
• Known allergy or hypersensitivity to study drugs or their excipients.
• Any condition that, in the investigator's judgment, would interfere with trial participation or interpretation of results.