Background: Colon cancer (CC) occurs in around 50% of the patients after 70 years. Adjuvant chemotherapy (CT) has demonstrated a benefit on disease-free survival (DFS) and overall survival after a stage III CC resection. Nevertheless, adjuvant CT is poorly used in elderly patients. There is still concern about the efficacy of doublet CT with oxaliplatin in fit elderly patients and the usefulness of fluoropyrimidine monotherapy in unfit elderly patients. The selection of patients that should be treated remains a challenge. Geriatric evaluation and tumor biology should be explored to help for patient selection. Methods: ADAGE is a multicenter, randomized phase III study comparing 3-years DFS of 2 therapeutic strategies in 2 groups of patients aged over 70 with completely resected stage III CC. Patients are included in one of the 2 groups after a multidisciplinary team evaluation; Group 1 (arm A and B) is defined as “able” to be treated with doublet CT; Group 2 (arm C and D) is defined as “unable” to be treated with doublet CT. In each group, patients are randomized according to a 1:1 ratio. Randomization is stratified according to center, gender, stage (IIIA vs IIIB vs IIIC), occlusion and/or perforation (yes vs no) and independent activity of daily living score (IADL: normal vs abnormal). Arm A and D receive LV5FU2 or capecitabine, arm B FOLFOX4 or XELOX and arm C is an observation arm. The treatment is planned for 6 months. Adjuvant CT should start within 12 weeks after surgery. Geriatric questionnaires and Lee score must be completed before randomization. Radiological assessment is performed every 6 months for 3 years after randomization and then annually for 2 years. Hypotheses (α two-sided = 5%, power = 80%) are to improve 3-years DFS from 65% (arm A) to 72% (arm B) in group 1 (756 patients required) and from 40% (arm C) to 55% (arm D) in group 2 (226 patients required). Safety is evaluated based on laboratory and clinical tests before each cycle. Exploratory analysis are planned to determine geriatric prognostic factors for DFS. A biological ancillary study is planned to allow prognostic evaluation of mismatch repair status and other molecular signatures. At the 1^stof February 2017 the accrual was 246 patients. Clinical trial information: NCT02355379