Birkman EM, et al. - Researchers analyzed epidermal growth factor receptor (EGFR) gene copy number (GCN) by EGFR immunohistochemistry guided silver in situ hybridization in primary and corresponding recurrent local or metastatic colorectal cancer tumors, and compared GCN levels between KRAS wild-type patients who had anti-EGFR therapy and patients who received other forms of treatment after primary surgery. Findings suggested an association of anti-EGFR antibody treatment with EGFR GCN decrease between the primary and recurrent colorectal adenocarcinomas. Among patients receiving other forms of treatment after primary surgery, no GCN change was noted. As compared to KRAS mutated tumors, wild-type KRAS tumors had higher EGFR gene copy number.