In a retrospective study of 170 patients with HNSCC, BRCA2 and ARID1A were found to be the two DDR genes with the highest mutation rates, with 17.6% of patients having mutations in these two genes, followed by ATM and BRCA1 with 13.5% and 10% mutations, respectively (28). Here, ATM is linked to head and neck squamous cell carcinoma.