Predictive marker for egfr inhibitor treatment

An in vitro method of predicting the response of a cancer patient to treatment with an epidermal growth factor receptor (EGFR) inhibitor comprising:

• determining an expression level of a protein tyrosine phosphatase Type IV A, member 1(PTP4A1) gene in a tumour sample of a cancer patient and comparing the expression level of the PTP4A1 gene in the tumour sample to a value representative of an expression level of the PTP4A1 gene in tumours of a population of patients deriving no clinical benefit from the treatment, wherein a lower expression level of the PTP4A1 gene in the tumour sample of the patient is indicative for patient who will derive clinical benefit from the treatment.