Enteral nutrition it a method that enables delivery of enteral nutritional compositions by the oral route or technological aids (probe and pump) in the stomach or small intestine. Enteral nutrition has contributed to the spread of awareness of the importance of adequate nutritional support in clinical medicine. The indications for its use are malnutrition in patients and any condition leading to the nutritional status collapse (Krznarić, 2008). The standard enteral diet supplemented with compositions containing omega-3-fatty acids in such patients may result in reduced weight loss, reduced complications of chemotherapy and radiotherapy, inhibition of inflammatory mediators and catabolic. (Krznarić, 2006). In oncologic patients most commonly associated symptom with their basic illness is the anorexia-cachexia syndrome. Its prevalence among tumor patients is between 8 and 88%. Cachexia occurs with the highest percentage of patients with head, neck, stomach and pancreas tumors. Tumor cachexia is most prominent in the terminal stage of the disease although it may sometimes appear at the beginning of the disease's manifestation. It is clinically manifested by anorexia, weight loss, the feeling of weakness, tiredness, loss of skeletal muscle mass and fat tissue, changes in carbohydrate metabolism, fat and protein, anemia, hypertriglyceridemia, hypoalbuminemia, and glucose intolerance. A major problem that occurs in cancer cachexia is the impossibility of enduring the active oncological treatment (Dintinjana, R. et al., 2015). As many as 20% of patients with cancer die of malnutrition and not as a result of the underlying disease (Krznarić, 2006).