Association of EGFR CA simple sequence repeat 1 (CA-SSR1) variant with cetuximab (cet)-induced skin toxicity (ST) in Japanese metastatic colorectal cancer (mCRC) patients (pts) with overexpressed EGFR and KRAS exon 2 wild-type (KRAS wt) (JACCRO CC-05/06 AR).

582 Background: Associations of EGFR gene copy number (GCN) and EGFR CA-SSR1 polymorphism with clinical outcome still remain controversial in mCRC pts treated with cet. Interethnic differences in the repeat number of EGFRCA-SSR1 have been reported between Caucasian and Asians, however, there have been few reports about the associations with clinical outcome in Japanese pts. The aim of this study was to evaluate the predictive value of two biomarkers in Japanese mCRC pts treated with cet. Methods: This study enrolled 77 pts with tumor available from two prospective clinical trials evaluating combination of cet with oxaliplatin-based chemotherapy as first-line treatment in mCRC pts with KRAS wt and EGFR-expressing tumors, modified FOLFOX6 (n=28/57, UMIN000004197) and SOX (n=49/67, UMIN000007022). Genomic DNA isolated by macro-dissection from tissue was screened for the EGFR GCN determined by FISH on FFPE tumor specimens with the cut-off value of 2.9, adopted as previously reported (Cappuzzo F, et al., 2008)...