3758 - Efficacy of Postoperative Radiotherapy Following Induction Immunochemotherapy and Surgical Resection in Locally Advanced Head and Neck Squamous Cell Carcinoma

Y. Xu¹, J. Wang¹, Y. Zhang¹, R. Wu¹, X. Chen¹, X. Huang¹, K. Wang¹, Y. Qu¹, Y. Ma¹, J. Luo¹, L. Gui², X. Wang³, 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): Induction chemotherapy is commonly used in head and neck squamous cell carcinoma (LA-HNSCC) whereas its effect on survival improvement is still under debate. Recently, the integration of induction immunotherapy and chemotherapy (IIC) holds promise for enhancing pathological response rates in LA-HNSCC, whilst with rare survival data being reported. Moreover, this novel modality of treatment promotes more challenges for the subsequent therapy, such as the indication and intensity of postoperative radiotherapy (PORT). This study aimed to evaluate the survival outcomes of LA-HNSCC patients treated with IIC followed by surgical resection and PORT. Materials/

Methods: Patients diagnosed with stage III-IVa HNSCC who underwent IIC followed by surgery were retrospectively screened, and only those who subsequently received PORT were included in the final analysis. The doublet regimen for induction chemotherapy was platinum-based. Overall survival (OS) and progression-free survival (PFS) rates were calculated using the Kaplan–Meier method. A univariable Cox proportional hazards regression model was used to examine correlations between survival and each covariate.
Results: A total of 26 patients received PORT following IIC and surgical resection between 2022 and 2023 at our center, with primary tumors predominantly located in the hypopharynx (12, 46.2%), oropharynx (5, 19.2%), and oral cavity (6, 23.1%). Eight patients were positive for HPV16. Nineteen patients had available CPS data, of which 11 had CPS scores = 20 and 8 had CPS scores between 1 and 19. All patients underwent at least 2 cycles of IIC, resulting in an 84.6% down-staging rate. Pathological complete response (PCR), major pathological response (MPR), and intermediate pathological response (IPR) rates were 34.6% (9), 23.1% (6), and 42.3% (11), respectively. The median follow-up duration was 18 months (range: 6-28 months). Both median progression-free survival (PFS) and OS were not reached. The estimated 1-year and 2-year PFS rates were 91.7% and 85.1%, respectively. The 1-year and 2-year OS rates were 95.8% and 89%, respectively. Only 1 patient experienced local recurrence, and one succumbed to metastasis. No grade 4 treatment-related toxicities were observed. Patients with pCR or MPR had much better PFS than those with IPR (p=0.022), while no significant statistical difference was detected in OS (p=0.059).
Conclusion: PORT demonstrated efficacy and safety in patients with advanced HNSCC. IIC achieved a higher rate of pathological response compared to historical data on neoadjuvant chemotherapy alone. Our cohort exhibited more favorable survival outcomes compared with historical data. Furthermore, a better pathological response predicts significantly better survival. Therefore, de-escalation of PORT may reduce treatment toxicity without compromising survival for these patients, warranting further investigation.