MSC (Avemar) is a medical nutriment of which preclinical and observational clinical studies suggested an antimetastatic activity with no toxicity. This open-label cohort trial has compared anticancer treatments plus MSC (9 g once daily) vs anticancer treatments alone in colorectal patients, enrolled from three oncosurgical centres; cohort allocation was on the basis of patients' choice. Sixty-six colorectal cancer patients received MSC supplement for more than 6 months and 104 patients served as controls (anticancer therapies alone): no statistical difference was noted in the time from diagnosis to the last visit between the two groups. End-point analysis revealed that progression-related events were significantly less frequent in the MSC group (new recurrences: 3.0 vs 17.3%, P<0.01; new metastases: 7.6 vs 23.1%, P<0.01; deaths: 12.1 vs 31.7%, P<0.01). Survival analysis showed significant improvements in the MSC group regarding progression-free (P=0.0184) and overall survivals (P=0.0278) probabilities. Survival predictors in Cox's proportional hazards were UICC stage and MSC treatment. Continuous supplementation of anticancer therapies with MSC for more than 6 months is beneficial to patients with colorectal cancer in terms of overall and progression-free survival.