Efficacy and safety of tislelizumab combined with chemoradiotherapy in high-risk locoregionally advanced nasopharyngeal carcinoma.

e18071 Background: The poor prognosis of high-risk locoregionally advanced nasopharyngeal carcinoma (LANPC) due to the high incidence of metastasis or local recurrence despite the development of radiotherapy. Immunotherapy has potential efficacy for LANPC, but the optimal treatment model remains unclear. This trial aimed to evaluate the efficacy and safety of tislelizumab combined chemotherapy in patients with high-risk LANPC. Methods: Patients with LANPC (stage III-IVa, AJCC 8th edition, except T3N0-1) were enrolled. All eligible patients received three 21-day cycles of induction treatment (Tislelizumab 200 mg intravenously on D1, gemcitabine 1g/m 2 intravenously on D1 and D8, and cisplatin intravenously 25 mg/m 2 , on D1 to 3) prior to cisplatin concurrent chemoradiotherapy. Adjuvant therapy included eight 21-day cycles (Tislelizumab 200 mg intravenously on D1 and capecitabine 1000mg/m 2 orally twice daily on D1 to 14). The primary endpoint was complete response (CR) rate after induction treatment. Secondary endpoints included objective response rate (ORR) after induction treatment, locoregional failure-free survival (LRRFS), distant metastasis-free survival (DMFS), failure-free survival (FFS), and safety. Results: Between Aug 2024 and Dec 2025, 33 patients were enrolled. As of Jan 2026, 30 patients completed induction treatment and were evaluated. The CR rate after induction treatment was 36.7% (11/30). The overall response rate (ORR) after induction treatment was 93.3% (28/30). The most common treatment-related adverse events were leukopenia, lymphopenia, nausea, transaminitis and anaemia. A few immune-related adverse events such as hypothyroidism, rash and allergic reaction were observed. No grade 5 adverse events occurred. Conclusions: Tislelizumab with standard GP chemotherapy followed by cisplatin concurrent chemoradiotherapy and adjuvant tislelizumab with capecitabine has achieved potential complete response rate and manageable toxicity in patients with LANPC in this trial. Treatment is continued and long-term follow-up is ongoing. Clinical trial information: ChiCTR2400084683.