Clinical Predictors of Cetuximab for First-Line Therapy of Metastatic Colorectal Cancer: A Single Institutional Retrospective Study

Abstract

Predictive factors of cetuximab efficacy for metastatic colorectal cancer (mCRC) have not been sufficiently revealed. The present study aimed to explore new predictors. A total of 30 patients with KRAS exon 2 wild-type unresectable mCRC, who had been treated with cetuximab-based regimen as first-line therapy, were retrospectively analyzed. We assessed whether gender, age, primary tumor site, RAS genotype, the Eastern Cooperative Oncology Group Performance Status (ECOG PS), metastatic status, histological grade, carcinoembryonic antigen (CEA), treatment regimen, and oxaliplatin-based adjuvant chemotherapy at baseline were associated with cetuximab efficacy. Progression-free survival (PFS) and objective response rate (ORR) were evaluated and statistically analyzed. Analysis of PFS revealed that left-sided tumor and good PS had relevance to good results. PFS among patients with left-sided CRC was longer than that among those with right-sided CRC (median, 10.6 and 3.5 months, respectively). Patients with a PS of 0 -1 experienced significantly longer PFS than those with a PS of 2 -3 (median, 8.6 versus 1.3 months, respectively). In analysis of ORR, high histological grade and serum CEA level showed interaction with good effect. Patients with histological grade I/II cancer experienced better ORR than those with histological grade III/IV cancer (76% versus 20%, respectively). ORR among patients with serum CEA level higher than 5.0 ng/ml was significantly higher than that among those with lower serum levels (88% versus 38%, respectively). ECOG PS, tumor location, histological grade, and serum CEA level at baseline might be useful predictors of cetuximab efficacy in the first-line treatment of mCRC.