Dosing to rash? - The role of erlotinib metabolic ratio from patient serum in the search of predictive biomarkers for EGFR inhibitor-mediated skin rash

The erlotinib/O-desmethyl-erlotinib metabolic ratio reflecting the individual metabolic activity of erlotinib correlated with the severity of skin rash and outcome in patients treated with EGFR tyrosine kinase inhibitors. The metabolic ratio determined in serum may be used for therapeutic monitoring in erlotinib treatment and decisions on individual dosing to rash in rash-negative patients.