Plain English summaryRecurrent/metastatic head and neck squamous carcinoma (R/M HNSCC) patients face limited treatment choices and poor prognosis. As a new treatment method, immune checkpoint inhibitor plays an important role for the R/M HNSCC patients recently. However, there were still some controversies for the combination of chemoradiotherapy and immunotherapy, such as timing, radiation dose, fractionation, and et al. In our study, the synergy of concurrent chemoradiotherapy with PD-1 inhibitor showed a promising results for the R/M HNSCC patients, with improved objective response rate (ORR) (70.0%, 95% CI 55.8% to 84.2%) and disease control rate (DCR) (100%, 95% CI 100% to 100%). The median progression-free survival (PFS) and overall survival (OS) were prolonged to 9 months (range 3.1-14.9 months) and 19 months (range 6.3-31.7 months) respectively. The toxicity was tolerable during the treatment, the total incidence rate of grade 3 or 4 adverse events were 65%, similar with other study. BackgroundProgrammed cell death-1 (PD-1) inhibitor was proven to be useful for the recurrent/metastatic head and neck squamous carcinoma (R/M HNSCC) patients. Though both PD-1 inhibitor alone and combination with chemotherapy showed some benefit for PFS and OS, the survival outcome was still not satisfactory. Some studies showed the possible benefit for PD-1 inhibitors combination with radiation for head and neck squamous carcinoma, however there was few studies concerned about synergy of concurrent PD-1 inhibitor combination with chemoradiotherapy for R/M HNSCC. So, we aimed to explore the potential effect and toxicity of the concurrent PD-1 inhibitor and chemoradiotherapy for R/M HNSCC.MethodsWe consecutively enrolled the R/M HNSCC patients treated with concurrent PD-1 inhibitor and chemoradiotherapy from August 2018 to April 2022 in Sichuan Cancer hospital. All the patients received the combination of PD-1 inhibitor and chemotherapy, and followed with synergy of concurrent PD-1 inhibitor and chemoradiotherapy, then maintenance PD-1 inhibitor. ORR and DCR was calculated by immune-related Response Evaluation Criteria in Solid Tumors (irRECIST-1.1), and Common terminology criteria for adverse events (CTCAE-4.0) was used to evaluate the toxicity.The Kaplan-Meier method was used to analyze OS and PFS.Results40 R/M HNSCC patients were enrolled in our stuty. The median follow up time was 14 months. 22 patients had recurrent disease only, 16 patients had metastatic disease only, and 2 patients had both recurrence and metastasis disease. For the recurrent lesions, 23 patients received a median radiation dose of 64 Gy (range 50-70 Gy). 18 patients received a median dose of 45 Gy (range 30-66 Gy) for metastatic lesions. The median courses of PD-1 inhibitors and chemotherapy were 8 and 5 respectively. After the treatment, the ORR and DCR were 70.0% and 100%. The median OS was 19 months (range 6.3-31.7 months), with 1 and 2-years OS rates of 72.8% and 33.3%. The median PFS was 9 months (range 3.1-14.9 months), with 6 and 12 months PFS rates of 75.5% and 41.4% respectively. The PFS had no statistical significance in PD-L1 negative and positive group (7 vs 12 months, p = 0.059). The most common grade 3 or 4 adverse events(AE) were leucopenia (25.0%), neutropenia (17.5%), anemia (10.0%), thrombocytopenia (5.0%), hyponatremia (2.5%), and pneumonia(2.5%). No grade 5 AE was observed.ConclusionsThe synergy of concurrent PD-1 inhibitor treatment with chemoradiotherapy shows promise as a treatment strategy and an acceptable toxicity for the R/M HNSCC patients.