Methods are provided for facilitating the diagnosis of subjects with HER1-activated cancers. In addition, method of treating subjects with a cancer characterized as having high levels of activated HER1 are provided. Also provided are methods for determining or otherwise assessing the prognosis of an subject with a HER1-activated cancer. The methods include the analysis of samples for the presence or the absence of activated HER1 markers as indicated by HER1-HER1 homodimers, HER1 phosphorylation at position 1173, pan-phosphorylation of HER1 or associated molecules, or HER1-HER2 heterodimers. Activated HER1 measurements can be used to track a subjects response to a treatment regimen, predict the success of using a particular treatment regimen, determine the effects of a treatment regimen, or for categorizing a subject in order to create a homogenous group for a clinical trial.
