Background: Clinical trials have not yet shown convincingly if adjuvant chemotherapy is justified for stage II CC patients of whom 25% are at risk of recurrence. An 18-gene expression profile, ColoPrint, has been developed for identifying CC cancer patients more likely to develop recurrent disease and who would be candidates for adjuvant chemotherapy. The gene signature has been validated in independent cohorts of 206 CC patients and in in-silico datasets (Salazar et al, JCO in press). The profile classified 63.2% of the stage II patients (n=134) as low risk. The HR for relapse free survival (RFS) was 3.34 (p=0.017) with a 5-year RFS rate of 90.9% (95%CI, 84.0 -97.8%) for low risk patients and 73.9% (95%CI, 59.2-88.6%) for high risk patients. 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. The main objectives are: (1) determine risk assessment by ColoPrint profile versus clinical parameters based on local protocol and ASCO high-risk recommendations in stage II patients; (2) establish proportion of 'good prognosis' and 'poor prognosis profile' in various countries; and (3) validate the power of risk assessment and compare performance of ColoPrint and clinical risk assessment in estimating 3 year relapse rate. Inclusion criteria: age ≥ 18 years, adenocarcinoma of the colon, stage II, no neoadjuvant systemic therapy, no synchronous tumors, fresh tumor sample, and written informed consent. The treatment of the patient is at the discretion of the physician. Results: The trial started in Sept. 2008 with currently 26 participating sites in 11 countries. So far, 223 stage II patients have been enrolled of whom 183 are eligible. 11 patients were rejected because of prior malignancies; 24 patients were rejected based on low tumor content of the sample (< 30% tumor cells), 3 patients had rectal cancer and 2 synchronous tumor. Conclusions: The aim is to enroll 600 stage II patients to differentiate between 3 year relapse- free survival predicted by ColoPrint versus clinical factors.