EGFR biomarkers useful in a method for predicting the likelihood that a mammal that will respond therapeutically to a method of treating cancer comprising administering an EGFR modulator, wherein the method comprises (a) measuring in the mammal the level of at least one biomarker selected from epiregulin and amphiregulin, (b) exposing a biological sample from the mammal to the EGFR modulator, and (c) following the exposing of step (b), measuring in the biological sample the level of the at least one biomarker, wherein an increase in the level of the at least one biomarker measured in step (c) compared to the level of the at least one biomarker measured in step (a) indicates an increased likelihood that the mammal will respond therapeutically to the method of treating cancer.