EGFR and head and neck squamous cell carcinoma: In fact, results from the randomized clinical trial (NCT00779389) involving the first HNSCC exceptional responder eventually concluded that baseline tumoral p-MAPK (p-ERK) levels were inversely correlated with tumor size post-erlotinib treatment, showing that MAPK activation status is likely an indicator of EGFR-addiction in HNSCC, and thus predictive of clinical responses to erlotinib in HNSCC patients62.