Use of adjuvant chemotherapy (AC) and outcomes in stage II colon cancer (CC) with versus without poor prognostic features.

Abstract

338 Background: AC is frequently considered in patients (pts) with "high risk" stage II CC, defined by the presence of >/=1 poor prognostic features such as obstruction or perforation, T4 stage, <12 lymph nodes removed, positive resection margins, and lymphovascular or perineural invasion. Survival benefits associated with AC use in high risk pts remain largely unproven. Our aims were to examine patterns of AC use in stage II CC and to explore the impact of AC on survival in high vs. low risk pts. Methods: All pts with stage II CC in British Columbia from 1999 to 2008 and evaluated at 1 of 5 regional cancer centers were reviewed. Kaplan-Meier and Cox regression methods were used to correlate high vs. low risk status and receipt of AC with relapse-free (RFS), disease-specific (DSS), and overall survival (OS). Results: We identified 1,697 pts: 1,236 (73%) high risk and 461 (27%) low risk among whom 363 (29%) and 61 (13%) received AC, respectively. Individuals with high risk disease who received AC were younger (median 62 vs. 72 yrs, p<0.01) and had better performance status (ECOG 0/1 47% vs. 34%, p=0.02). For high risk pts, AC was associated with improved 5-year OS (Table). Adjusting for confounders, an OS advantage from AC persisted for high risk pts (HR 0.67, 95CI 0.52-0.86, p=0.002), with no significant RFS or DSS benefits. Subgroup analyses revealed individuals with T4 lesions had significantly improved RFS (HR 0.63, 95CI 0.42-0.95, p=0.03), DSS (HR 0.59, 95CI 0.37-0.93, p=0.03), and OS (HR 0.50, 95CI 0.33-0.77, p=0.002). For low risk pts, AC was associated with worse RFS (HR 2.27, 95CI 1.03-4.97, p=0.04) and DSS (HR 2.97, 95CI 1.10-8.02, p=0.03). Conclusions: In this population-based cohort study, AC was associated with an OS advantage in high risk pts, likely due to pt selection. RFS and DSS benefits were mainly seen in T4 lesions, suggesting a limited role for AC in pts deemed high risk. A possible trend towards harm was seen in the low risk group receiving AC. Better risk stratification schemes including those that incorporate molecular testing are warranted. [Table: see text]