The Use of Combination Palliative Radiotherapy and Single‐Agent Immunotherapy for the Management of Head and Neck Squamous Cell Carcinoma ( HNSCC ) in the United Kingdom ( UK )

Clinical data on combined Immunotherapy (IO) and palliative radiotherapy (RT) in HNSCC is scarce. HNSCC Palliative RT differs from curative intent RT as it does not involve elective nodal irradiation; therefore, an immune response may be more likely. We conducted a UK retrospective survey of patients starting palliative RT and IO monotherapy within 3 months of each other. About 75 patients were treated at 16 centres from January 2022 to December 31, 2023. About 89.3% received first‐line Pembrolizumab and 10.7% second‐line Nivolumab. 13.3% reported ≥ Grade 3 immune‐related adverse events and 6.7% ≥ Grade 3 RTOG side effects; overall response rate (ORR) was 41.3%. Median overall survival (OS) was 10.2 months (95% CI: 6.5–16.2) and median progression‐free survival (PFS) was 5.6 months (95% CI: 4.8–8.3). OS was significantly better in locally advanced disease non‐amenable to radical treatment (OS HR = 0.42 (95% CI: 0.18–0.97), p = 0.043) and de‐novo metastatic disease (OS HR = 0.35 (95% CI: 0.16–0.76), p = 0.008) compared to recurrent disease. Compared to starting IO > 6 weeks after radiotherapy initiation, OS was significantly better in those starting IO 0–6 weeks after radiotherapy initiation (OS HR = 0.40 (95% CI: 0.17–0.95), p = 0.037). The ORR in this cohort is higher than published data of single agent IO alone. Improved survival outcomes in patients receiving IO closer to RT with BED > 70 and alternative fractionation may reflect favourable patient selection but could be influenced by synergy between IO and RT. These findings are from non‐randomised cohort data and should be seen as exploratory and hypothesis generating.