Background: The IDEA collaboration pooled data from nearly13,000 patients (pts), comparing 3 vs. 6 months (m) of adjuvant fluoropyrimidine plus oxaliplatin to test noninferiority for disease-free survival (DFS) in stage III colon cancer. We reported that duration of adjuvant therapy (Rx) should be individualized with consideration of recurrence risk, regimen, and toxicity. Here we consider the influence of age, gender, and PS. Methods: Using stratified Cox proportional hazard models we stratified the IDEA cohort by age (≤ 70 or > 70), gender, and PS (0 v 1/2), testing for interactions with subgroups and duration of Rx. Results: Overall, DFS results comparing 3 vs 6m of Rx did not significantly differ across age, gender or PS subgroups. However, significant (sig) interactions were detected within subgroups (Table). For pts ≤ 70 who received CAPOX, 3m Rx is as good as 6m (HR 0.9). 6m of Rx is required for pts ≤70 (HR 1.16) with FOLFOX and may be best for pts > 70 on either regimen (p = .068, 3 way interactions). It was found that gender influenced the impact of risk group on the duration comparison (p = .078, 3 way interaction); 3m Rx was as good as 6m for male low-risk pts (HR 0.94) but 6m is required for high risk male (HR 1.18). For females, risk group did not alter the relative merits of 3 v 6m of Rx. PS did not influence the impact of regimen/risk group on the duration comparison. Conclusions: Overall age, gender, or PS didn’t modify the comparison of 3 v 6m Rx. The biologic and clinical rationales for the differences observed within certain subgroups need to be explored before they are used to make treatment choices. Clinical trial information: NCT01150045