The ORRs were 7.8% for durvalumab + tremelimumab, 9.2% for durvalumab, and only 1.6% for tremelimumab alone, demonstrating for the first time that CTLA-4 inhibition might contribute to enhanced toxicity and not to an improvement of response in SCCHN. This evidence concerns the gene CTLA4 and head and neck squamous cell carcinoma.