Impact of high-risk features on disease-free survival (DFS) in patients (pts) with high-risk stage II colon cancer (CC) in ACHIEVE-2 trial as part of the IDEA collaboration

4011 Background: The IDEA collaboration for high-risk stage 2 colorectal cancer patients (pts) demonstrated that for CAPOX, 3 months was non-inferior to 6 months treatment, while for FOLFOX, 6 months was superior to 3 months treatment. We investigated the impact of high risk features on disease-free survival (DFS). Methods: ACHIEVE-2, one of the 4 IDEA studies (SCOT, TOSCA, ACHIEVE-2, HORG), was an open-label, multicenter randomized trial for high-risk stage II colon cancer. High risk features are defined as one or more: T4, inadequate nodal harvest < 12, poorly differentiated, clinical sign of obstruction and perforation or vascular invasion. The association of high risk features with DFS were measured by Cox regression analyses. Results: Between 2014 and 2017, ACHIEVE-2 enrolled 525 pts, out of whom 514 pts were the modified ITT (mITT) population; 432 received CAPOX (84.0%) and 82 did mFOLFOX6 (16.0%). High-risk features included 35.8% of T4, 12.8% of inadequate nodal harvest, 11.5% of poorly differentiated, 19.3% of obstruction, 6.4% of perforation and 87.5% of vascular invasion; 47.3% had one features, 35.2% had two, 14.6% had three, and 2.9% had four or more. With a median follow-up of 36.1 months, 3-year DFS rates were 88% in both arms, with a hazard ratio (HR) of 1.12 (95% CI, 0.67-1.87, p=0.67). In multivariate analysis, T4 (HR 3.77 [2.18-6.53], p< 0.0001) and inadequate nodal harvest (HR 2.98 [1.59-5.59], p= 0.0006) remained independent significant negative prognostic factors. The 3-year DFS rates in T4 and Non-T4 diseases were 78% and 94% (p