Primary resistance to CTX is mainly due to aberrations in the KRAS, NRAS, and EGFR genes [13], which are often found in other cancer backgrounds, including colorectal cancer (CRC) and non-small cell lung cancer (NSCLC) but are uncommon in HNSCC tumours in CTX-naïve patients [14]. This evidence concerns the gene KRAS and non-small cell lung carcinoma.