It is Randomized Controlled Trial, in which investigators will estimate the impact of the use of immunonutrition support compared to standard nutritional support in the preoperative period in patients with colorectal cancer.

The first choice of treatment in colorectal cancer is surgery. Nutritional support in form of oral nutritional supplements (ONS) in the preoperative period is widely accepted in reducing the incidence of perioperative complications and immunonutrition is generally recommended. However, there is little clinical data regarding the impact of such treatment on a tumor biology.

Investigators want to perform Randomized Controlled Trial to explore the impact of the use of immunonutrition in relation to standard nutritional support in the preoperative period on alternating the expression of inflammatory response cytokines expression and leukocytes infiltration in tumor tissue in patients operated for colorectal cancer.

Inclusion Criteria:

• Diagnosis of colon cancer during preoperative colonoscopy confirmed by histopathological examination.

Exclusion Criteria:

• emergency/urgent operation
• active infection
• inflammatory bowel diseases in history
• other systemic immune disorders
• the necessity of preoperative neoadjuvant treatment (radiotherapy or chemotherapy)
• metastatic disease, or local infiltration of cancer which was described as T4 stage in preoperative CT scan
• patients who were not able to intake at least 85% of administrated ONS doses