Updated results of adjuvant toripalimab for locally advanced head and neck squamous cell carcinoma patients who achieved pathological complete response after neoadjuvant immunochemotherapy and surgery: A single-arm, phase II trial.

e18097 Background: Neoadjuvant immunochemotherapy (NICT) showed favorable efficacies and anticipated outcomes for locally advanced head and neck squamous cell carcinoma (LA-HNSCC). However, optimal adjuvant therapy remains uncertain for LA-HNSCC patients who achieved pathological complete response (pCR) after NICT and surgery. This study aims to explore an optimal adjuvant strategy with low-toxicity and survival benefits for these patients. Preliminary results were presented at the 2024 ESMO Congress (Poster 865P), and the consecutively updated results were presented in this report. Methods: In this single-arm, phase II trial, 27 LA-HNSCC patients were planned to be enrolled. Key inclusion criteria were: pathologically confirmed LA-HNSCC patients (stage III-IVB for non-oropharyngeal cancers and HPV-negative oropharyngeal cancer; stage II-III or stage I with adverse features for HPV-positive oropharyngeal cancer, according to the 8th edition of the AJCC staging manual), receipt of at least 1 cycle of NICT (platinum-based chemotherapy and anti-PD-1 immunotherapy) and surgical resection, and achievement of pCR to the primary tumor and regional lymph nodes. Eligible patients received adjuvant immunotherapy with toripalimab (240mg) on day 1 of each 21-day cycle for 8 cycles. The primary end point was 2-year disease-free survival rate. Secondary end points included 2-year overall survival rate, 2-year disease specific survival rate, quality of life, and safety. Results: From Jan 2023 to Nov 2024, a total of 27 patients were enrolled and 24 finished the planned therapy. The median age was 52 years (29-75) and 88.9% were males. After a median follow-up time of 17.7 months, 2 (7.4%) patients suffered local recurrence, one underwent salvage surgery, and one underwent chemotherapy combined with cetuximab. No deaths occurred. Most common treatment-related adverse events (TRAEs) included increased blood creatinine (18.5%), hypothyroidism (14.8%), and skin toxicity (11.1%). 2 (7.4%) patients experienced grade 3 TRAEs including 1 (3.7%) anaemia and 1 (3.7%) ulcerative colitis. Conclusions: The preliminary results highlighted that adjuvant toripalimab for LA-HNSCC patients who achieved pCR after NICT and surgery showed encouraging efficacy and tolerable toxicity. Furthermore, these conclusions required to be confirmed in subsequent trials. Clinical trial information: ChiCTR2300067960 .