3752 - The Efficacy of PD-1 Inhibitor and Induction Chemotherapy Followed by Radical Radiotherapy in Locally Advanced Head and Neck Squamous Cell Carcinomas

J. Wang¹, Y. Meng¹, Y. Zhang¹, R. Wu¹, L. Gui², X. Chen¹, X. Huang¹, K. Wang¹, Y. Qu¹, Y. Ma¹, J. Luo¹, S. Liu³, and J. Yi¹; 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 and Peking Union Medical College, Beijing, China, ³Department of Head and Neck Surgical Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China

Purpose/Objective(s): The role of induction chemotherapy (IC) in locally advanced head and neck squamous cell carcinoma (LA-HNSCC) is controversial because there was no explicit evidence of prolonged survival from IC. Recent studies have shown that PD1 inhibitor in addition to IC could achieve unprecedented pathological response in LA-HNSCC. However for patietns who did not receive subsequent surgery due to varied reasons, there is lack of response and survival data. Therefore, this study aims to investigate the efficacy of induction immunotherapy and chemotherapy (IIC) followed by radical radiotherapy in patients with LA-HNSCC. Materials/

Methods: Patients with histopathologic confirmed LA-HNSCC who received IIC were routinely assessed in the multidisciplinary team to determine the subsequent treatment approach. Radical radiotherapy was recommended in view of, the following conditions, such as notable tumor reduction, surgical ineligibility due to persistent unresectability or comorbidities, as well as the decision for larynx preservation despite poor tumor response.
Results: The cohort comprised 68 patients who underwent radical radiotherapy following IIC at our institution from October 2021 to December 2023. The median age was 59 (40-73) years and only 3 patients (4.4%) were female. The predominant primary site of tumors was hypopharynx (45.6%), followed by oropharynx (32.4%), oral cavity (8.8%), larynx (8.8%). Accroding to AJCC 8th edition, there were 16 (23.5%) patients with stage III diseases, including 8 with P16+ oropharyngeal cancer (OPC), and 52 (76.5%) with stage IV diseases. The median cycles of induction therapy was 3 cycles (Range: 1 - 6) and 85.3% of patients underwent 2 or 3 cycles. Concurrent chemotherapy was utilized in 49 (58.8%) patients during radiotherapy. The median RT dose was 69.96 Gy (Range: 49.68 to 70) to the gross tumor lesion and 60.06 Gy to the clinical tumor volume, without shirkage of the radiation volume regardless of the response to IIC. We observed impressive response rates, with an objective response rate (ORR) of 88.2% after IC and 94.1% following radiotherapy. Over a median of 8.5-month and the shortest of 6-month follow-up, one-year overall survival (OS), progression-free survival (PFS), locoregional progression-free survival (LRFS) rates were 94.2%, 73.8%, and 84.0%, respectively. Up to the last follow-up, no patients underwent salvage surgery, resulting in a 100% of laryngeal preservation (LP). This multidiciplinary modality of treatment was generally well-tolerated, though 10 (14.7%) patients experienced grade 3-4 treatment-related adverse events (TRAEs) during IIC, primarily myelosuppression (14.7%).
Conclusion: Compared with historical data, the combination of induction immuno-chemotherapy and following radical radiotherapy exhibited excellent ORR, promising short-term survival outcomes and exceptional rates of LP. Long-term surveillance and further prospective study are warranted.