Background: An 18-gene expression profile, ColoPrint, has been developed for identifying CC patients more likely to develop recurrent disease and who would be candidates for adjuvant chemotherapy. The gene signature was validated in in-silico datasets and independent patient cohorts of stage II and III patients. Uni-and multivariate analysis was performed on the pooled stage II patient set (n=320) who had a median follow-up of 70 months. ColoPrint identified two-third of the stage II patients (209/320) as low risk. The 3-year relapse-free survival was 94% for Low Risk patients and 79% for High Risk patients with a HR of 2.74 (95% CI 1.54 - 4.88; p=0.006). Moreover, the profile stratified patients independent of ASCO clinical risk factors. Methods: A prospective trial, PARSC (Prospective study for the Assessment of Recurrence risk in Stage II CC patients) using ColoPrint has been initiated. Objectives are: (1) to validate the performance of ColoPrint in estimating the 3-year relapse rate in patients with stage II colon cancer; (2) to compare the risk assessment in stage II patients using the ColoPrint profile vs. a clinical risk assessment based on Investigator’s assessment of risk and ASCO high-risk recommendations; (3) to investigate therapy as a potential confounding factor for ColoPrint results; and (4) to assess the performance of ColoPrint in estimating the 3-year relapse rate in patients with stage III colon cancer. Inclusion criteria: age ≥ 18 years, adenocarcinoma of the colon, stage II and III, no prior neo-adjuvant therapy, no synchronous tumors, fresh tumor sample, and written informed consent. The treatment of the patient is at the discretion of the physician adhering to National Comprehensive Cancer Network (NCCN)-approved regimens or a recognized alternative. Results: The trial started in Sept. 2008 with currently 30 participating sites in 11 countries. Thus far, 288 eligible stage 2 and 251 stage 3 patients have been enrolled. Conclusions: The aim is to enroll 575 stage II patients to differentiate between 3 year RFS predicted by ColoPrint and clinical factors.