Weight loss, an indicator of malnutrition, is a common problem in cancer patients that is due to primary effect of abnormal metabolism by cancer cells, and to secondary effects of cancer therapy such as chemotherapy and radiation therapy. These therapies in cancer patients cause various symptoms including anorexia, nausea, vomiting, diarrhea, constipation, mucotitis, and alterations in taste and smell, etc. These symptoms are also reasons for weight loss. Weight loss has been recognized as an important component of adverse outcomes, including decreased response to chemotherapy, quality of life(QOL), and increased morbidity and mortality. Therefore, early recognition and detection of risk for malnutrition through nutritional assessment and administration of appropriate nutritional care including parenteral nutrition should be required throughout cancer care. Good nutrition management can help cancer patients prevent weight loss, and improve therapeutic response, prognostic implication, and QOL