EGFR gene copy number decreases during anti-EGFR antibody therapy in colorectal cancer

摘要

Epidermal growth factor receptor (EGFR) gene copy number (GCN) increase is associated with a favorable anti-EGFR antibody treatment response inRASwild-type metastatic colorectal cancer. However, there are limited and comparative data regarding theEGFRGCN in primary colorectal cancer tumors and corresponding metastases or the effect of anti-EGFR antibody treatment onEGFRGCN in recurrent disease. In addition, little is known about the potentialEGFRGCN changes during anti-EGFR therapy in comparison with other treatment regimens.EGFRGCN was analyzed by EGFR immunohistochemistry-guided silver in situ hybridization in primary and corresponding recurrent local or metastatic tumors from 80 colorectal cancer patients. GCN levels were compared betweenKRASwild-type patients having received anti-EGFR therapy and patients having received other forms of treatment after primary surgery. TheEGFRGCN decrease between primary and recurrent tumors was more pronounced among the anti–EGFR-treated patients than among patients not treated with anti-EGFR therapy (P= .047). None of the patients experiencing anEGFRGCN increase of at least 1.0 between the primary and recurrent tumors were treated with anti-EGFR antibodies. When including only patients with distant metastases, anEGFRGCN decrease of at least 1.0 was more common among the anti–EGFR-treated patients than among patients not treated with anti-EGFR therapy (P= .028). Our results suggest that anti-EGFR antibody treatment is associated withEGFRGCN decrease between the primary and recurrent colorectal adenocarcinomas, whereas no GCN change is observed among patients receiving other forms of treatment after primary surgery.