Anti-PD-1 immunotherapy with dose-adjusted ultra-hypofractionated re-irradiation in patients with locoregionally recurrent head and neck cancer

INTRODUCTION: Patients with recurrent inoperable squamous-cell head-neck cancer (HNSCC) after chemo-radiotherapy have an ominous prognosis. Re-irradiation can be applied with some efficacy and high toxicity rates. Anti-PD-1 immunotherapy is effective in 25% of patients. Immunogenic death produced by large radiotherapy (RT) fractions may enhance immune response. MATERIALS AND METHODS: We evaluated the efficacy and tolerance of ultra-hypofractionated immuno-radiotherapy (uhypo-IRT) in 17 patients with recurrent HNSCC and 1 with melanoma. Four of HNSCC patients also had oligometastatic disease. Using a dose/time/toxicity-based algorithm, 7, 7 and 4 patients received 1, 2 and 3 fractions of 8 Gy to the tumor, respectively. Nivolumab anti-PD-1 immunotherapy was administered concurrently with RT and continued for 24 cycles, or until disease progression or manifestation of immune-related adverse events (irAEs). RESULTS: Early and late RT toxicities were minimal. Three patients developed irAEs (16%). After the 12th cycle, 7/17 (41.2%) and 5/17 (29.4%) patients with HNSCC showed complete (CR) and partial response (PR), respectively. CR was also achieved in the melanoma patient. The objective response rates in HNSCC patients were 57%, 86% and 66%, after 1, 2 and 3 fractions, respectively (overall response rate 70.6%). Most responders experienced an increase in peripheral lymphocyte counts. The median time to progression was 10 months. The 3-year projected locoregional progression-free survival was 35%, while the 3-year disease-specific overall survival was 50%. CONCLUSIONS: Anti-PD1 uhypo-IRT is safe and effective in patients with recurrent HNSCC. The high objective response rates and the long survival without evidence of disease support further trials on uhypo-IRT.