Neoadjuvant chemotherapy plus tislelizumab followed by concurrent chemoradiotherapy in patients with locoregionally advanced nasopharyngeal carcinoma: A single-arm, phase II trial

6068 Background: Neoadjuvant treatment with gemcitabine plus cisplatin (GP) prior to concurrent chemoradiotherapy (CCRT) has favorable survival outcomes with acceptable toxicity in patients with locoregionally advanced nasopharyngeal carcinoma (LANPC), 10% of whom achieved complete response (CR) after neoadjuvant treatment. Immune checkpoint blockade therapy plus GP regimen has been shown to improve the survival in recurrent or metastatic NPC. We investigated the efficacy and safety of neoadjuvant treatment with GP plus tislelizumab, an anti-PD-1 monoclonal antibody, in previously untreated LANPC. Methods: In this phase II, single-armed Simon two-stage study, eligible patients are of age 18-70, with adequate haematological, renal, and hepatic function, diagnosed with staged III-IVa（AJCC 8th） non-keratinizing LANPC. Enrolled patients received intravenous gemcitabine (1000 mg/m2) on days 1 and 8, cisplatin (80 mg/m2) on day 1, and tislelizumab (200mg) on day 1 every 3 weeks for 3 cycles followed by standard CCRT. The primary endpoint was CR rate after neoadjuvant treatment, using Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1 by investigator. The secondary endpoints included pathology complete response (pCR) rate, 2-year progress-free survival (PFS), overall survival (OS), locoregional failure-free survival (LRRFS), distant metastasis-free survival (DMFS), and toxicity. This study is registered with ClinicalTrials.gov, NCT04833257, all enrolled patients have finished their treatment and the follow-up is ongoing. Results: From April 14th 2021 to August 5th, 2021, a total of 63 patients (median age 46y, 74.6% male) were enrolled at Sun Yat-sen University Cancer Center. As of January 31st, 2022, the median follow-up is 7.37 months, no patients had disease progression. The CR rate after neoadjuvant treatment was 41.3% (95% CI, 28.8% to 53.8%). The ORR and pCR rate were 88.9% (95% CI, 80.9% to 96.9%) and 75.8% (95% CI, 64.8% to 86.8%), respectively. The incidence of acute treatment-related AEs (trAEs) and immune-related adverse events (irAEs) of grade 3 or 4 was 69.8% and 3.2%, respectively. All of irAEs for grade 3 or 4 were hepatotoxicity and skin rash. Long-term efficacy is awaited. Conclusions: Neoadjuvant treatment with GP plus tislelizumab achieved impressive CR rate and pCR rate with manageable toxicities. Further follow-up is needed to confirm the long-term efficacy. Clinical trial information: NCT04833257.