557P - Loss of CDX-2 expression is an independent poor prognostic biomarker in colorectal cancer

Loss of caudal-type homeobox transcription factor-2 (CDX-2) expression in colorectal cancers (CRC) has recently been proposed as a predictive biomarker for response to chemotherapy and also prognosis. However, the data on relationship between alterations in CDX-2 expression and clinicopathological variables remain limited. We herein aimed to investigate the clinicopathological factors and prognostic implications associated with loss of CDX-2 expression in CRC patients. Immunohistochemistry for CDX-2 expression was performed on formalin-fixed, paraffin-embedded tissue samples from 427 patients with CRC. Correlation between CDX-2 expression and clinicopathological characteristics were evaluated. Univariate and multivariate survival analyses were performed to reveal the prognostic value of loss of CDX-2 expression. Of 427 patients, 85% were stage I-III. Seventy six percent had left-sided primary tumors. Deficient mismatch repair (dMMR) was found in 12%. CDX-2-negative expression was identified in 18 out of 427 (4.2%) patients. Loss of CDX-2 expression was more commonly found in patient with right-sided tumors rather than left-sided tumors (9.4% vs 2.8% respectively, p=0.005) and dMMR compared to proficient MMR (11.5% vs 3.3% respectively, p=0.006). There was no association between CDX-2 expression and sex, stage, histologic subtype, tumor differentiation and lymphovascular/perineural invasion. By univariate analysis, patients with CDX-2 loss of expression had significantly worse overall survival (OS) and disease free survival (DFS) than those with CDX-2 positive expression (median OS 1.6 vs 11.6 months (mo), p