Adjuvant chemotherapy (AC) use and outcomes in stage II colon cancer (CC) with and without poor prognostic features.

Abstract

3527 Background: AC is frequently considered inpatients (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 retrieved, positive margins, and lymphovascular or perineural invasion. However, survival benefits associated with AC use in high risk pts remain largely unproven. Our aims were to 1) examine patterns of AC use in stage II CC and 2) explore the relationship between AC use and survival in high vs low risk pts. Methods: All pts diagnosed with stage II CC in British Columbia from 1999 to 2008 and evaluated at any 1 of 5 regional centers were reviewed. Kaplan-Meier and Cox regression methods were used to correlate a) high vs low risk status and b) receipt of AC with relapse-free (RFS), disease specific (DSS) and overall survival (OS). Results: We identified 1,697 stage II CC 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 features who received AC were younger (median 62 vs 72 years, p<0.001) and had better performance status (ECOG 0/1 47% vs 34%%, p=0.02). In the high risk group, AC was associated with improved 5-year OS, but not with RFS or DSS (Table). After adjusting for confounders, an OS advantage from AC persisted for high risk pts (HR 0.67, 95CI 0.52-0.86, p=0.002), but no significant RFS or DSS benefits were seen (HR 0.76, 95CI 0.58-0.99, p=0.05 and HR 0.75, 95CI 0.55-1.02, p=0.11, respectively). Subgroup analyses showed that individuals with T4 lesions had improved RFS (HR 0.63, 95CI 0.42-0.95, p=0.03), DSS (HR 0.59, 95CI 0.37-0.93, p=0.02), and OS (HR 0.50, 95CI 0.33-0.77, p=0.002). Conclusions: In this population-based cohort of stage II CC, 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 based on clinical and pathological factors. Risk stratification based on molecular testing should be further explored. [Table: see text]