Lyle, Stephen

443 Background: Identification of a sensitive and specific prognostic marker would aid in the management of patients (pts) with standard histopathology node negative colon cancer (CC). We conducted a pooled individual pt data analysis to confirm the prognostic value of GCC for disease recurrence in untreated stage II CC. Methods: GCC mRNA was quantified by RT-qPCR using formalin-fixed LN from 310 stage II pts diagnosed from 1991-2006 enrolled in two studies (Sargent 2011 [study1] and Haince 2009 [study2]). Patients were classified by GCC LN ratio (LNR) (high risk: LNR ≥ 0.1; low risk: LNR < 0.1), with LNR defined as number of GCC positive LN divided by number of informative LNs. Clinical outcomes included time to recurrence (TTR), overall survival (OS), disease-specific survival (DSS) and disease-free survival (DFS). Stratified log-rank tests and multivariate Cox models assessed the association between clinical outcomes and GCC LN status. Results: The 5-year recurrence rate in study 1 (n=241) was 15.8%, 24.9% in study 2 (n=69). GCC LNR high risk pts had significantly higher risk of TTR, OS, DSS and DFS, which remained after adjusting for age, T stage, grade, number of LNs examined, and presence of lymphovascular invasion ( Table ). In a secondary analysis of low risk stage II pts (T3, ≥12 LNs examined, and negative surgical margins, n=241), a strong relationship between GCC LNR and each endpoint remained (TTR HR=4.34, 95% CI=2.07 – 9.13, p<0.001). Conclusions: Pts with GCC LNR high risk status have significantly poorer outcomes compared to pts with low risk status, particularly among those traditionally considered to be low risk. [Table: see text]