EGFR ligands and ERCC1 mRNA expression to predict clinical outcome in Japanese (JPN) patients (pts) with metastatic colorectal cancer (mCRC) harboring overexpressed EGFR and KRAS exon 2 wild-type (KRAS wt) treated with cetuximab (cet) plus oxaliplatin-based chemotherapy (JACCRO CC-05/06 AR).

618 Background: Previous studies have reported that EGFR ligands, amphiregulin (AREG) and epiregulin (EREG), are potential predictive markers for cet and high ERCC1 expression is associated with resistance to platinum-containing chemotherapy. However, there are still few studies to assess predictive values of these expression levels in JPN mCRC pts. The aim of this study was to evaluate the values in JPN mCRC pts treated with cet. Methods: This study enrolled 77 pts with tissue available from 2 prospective clinical trials evaluating combination of cet with oxaliplatin-based chemotherapy as first-line treatment in pts with KRAS wt and EGFR-expressing tumors, modified FOLFOX6 (n=28/57, UMIN000004197) and SOX (n=49/67, UMIN000007022). Total RNA isolated by macro-dissection from tissue was screened by RT-PCR for mRNA expression levels of AREG, EREG, and ERCC1, the cut-off values of which were based on the optimal cut-off value using the maximal chi-square approach on tumor response with adjusted p values. The...