 150 Patients with histologically proven stage IV AJCC 7th Edition colorectal cancer CRC expressing wild-type KRAS or stage IV non-small cell lung cancer NSCLC expressing EGFR tested by immunohistochemistry IHC, with no previous exposure to Cetuximab or Panitumumab, who will receive treatment with an EGFR-antibody Cetuximab or Panitumumab. 