| Requirement |
1 | Histologically confirmed metastatic or unresectable colorectal cancer with known Kras status who will undergo first-line therapy. Knowledge of other mutations is optional. Participating investigator will select treatment, however, patients with Kras wild type must receive anti-EGFR therapy to be eligible for this study. |
2 | At least 18 years of age |
3 | Willing to follow study instructions for collection of specimens |
4 | Willing to undergo biopsy at the time of progression |
5 | Available archival tissue |
6 | Signed informed consent |
1 | Prior history of treatment for colon cancer |