Patients (pts) with available archival FFPE tumor tissue who received panitumumab or cetuximab ± chemotherapy at any time for treatment of mCRC at 8 UK cancer centers were eligible....AREG and EREG positive tumor cells were identified by IHC....110 (24.5%) received concomitant FOLFOX and 304 (67.7%) FOLFIRI. After adjustment for additional prognostic factors, high AREG/EREG expression (n = 360; 80.2%) was associated with significantly prolonged PFS (HR 0.73; 95% CI, 0.56-0.95; p = 0.02), OS (HR 0.66 [0.50-0.86]; p = 0.002), and DCR (OR 1.92 [1.05-3.54]; p = 0.04)....High tumor AREG/EREG expression was associated with significantly prolonged PFS, OS and DCR among a cohort of pts treated with anti-EGFR therapy during routine care of mCRC.