KRAS and head and neck squamous cell carcinoma: However, evidence that KRAS alterations, which are rare in HNSCC (~1.4%), are a marker for cetuximab response in HNSCC is inconsistent, as are the data on the impact of EGFR alterations on cetuximab response, highlighting the paucity of molecular markers available to guide the use of cetuximab for HNSCC treatment (27, 28).