3733 - Neoadjuvant Chemotherapy plus Tislelizumab Followed by Adjuvant Tislelizumab for Locoregionally Advanced Nasopharyngeal Carcinoma: A Single-Arm, Phase II Trial

S. Shiran¹, X. Huang¹, K. Wang¹, R. Wu¹, J. Wang¹, Y. Zhang¹, Y. Qu¹, X. Chen¹, J. Zhang¹, J. Luo¹, J. Yi¹, and S. Zhou²; ¹Department of Radiation Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China, ²Department of Medical Oncology, National Cancer Center/ National Clinical Research Center for Cancer/ Cancer Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, China

Purpose/Objective(s): The prognosis of nasopharyngeal carcinoma with T4 or N3 remains unsatisfactory. The aim of this study was to assess the efficacy and safety of neoadjuvant with GP plus tislelizumab followed by concurrent chemoradiotherapy, and adjuvant treatment with tislelizumab, an anti-PD-1 monoclonal antibody, in previously untreated stage IVA (T4 or N3) nasopharyngeal carcinoma. Materials/

Methods: In this phase II, single-arm study, eligible patients aged 18-70 years who were diagnosed with stage IVA (AJCC 8^th) non-keratinizing nasopharyngeal carcinoma received neoadjuvant therapy with gemcitabine (1000mg/m² on day 1,8), cisplatin (25 mg/m² on day 1-3) and tislelizumab (200mg) Q3W for 2 cycles followed by concurrent IMRT and cisplatin (100 mg/m²) Q3W during radiotherapy, then followed by adjuvant therapy with tislelizumab (200 mg) Q3W for 13 cycles. The primary endpoint was 2-year progression-free survival (PFS). The secondary endpoint included objective response rate (ORR), overall survival (OS) and safety.
Results: A total of 55 patients were enrolled from Sep. 2021 to Jun. 2023 with a median age of 43 (22-66) yrs and 76.4% (n=42) of male. T4 account for 43.6% and N3 account for 67.3%. After a median follow-up of 16 months, 7 patients experienced disease progression with one patient in local relapse, three patients in regional relapse and three patients in distant metastasis. One-year PFS rate was 89.7%, and 1-year OS rate was 100%. According to RECIST1.1, 48 (87.3%) patients had objective response to neoadjuvant treatment, including 9 (16.4%) patient with CR, 39 (70.9%) patients with PR. The other 7 (12.7%) patients had SDa with a definition of tumor shrinkage occured and below a 30% decrease in the sum of diameters of target lesions, taking as reference the baseline sum diameters. Throughout the neoadjuvant phase, 23 (41.8%) patients experienced grade 3-4 treatment-related adverse events (TRAE), with the most common being nausea (9[16.4%]) and leukopenia (8[14.5%]). Grade 3-4 TRAE appeared in 15 (27.3%) patients during concurrent chemoradiotherapy, with the most common being leukopenia (7[12.7%]) and mucositis (5[9.1%]).
Conclusion: For stage IVA nasopharyngeal carcinoma patients, neoadjuvant with tislelizumab plus GP and adjuvant tislelizumab treatment is safe and promising. Further follow-up is needed to confirm the long-term efficacy.