The target population in the present study is Chinese patients with oral and oropharyngeal cancer who plan to receive radio(chemo)therapy after surgical resection in the outpatient department. Investigators hypothesize that early enteral nutrition intervention, which is initiated 2 weeks before the start of postoperative radio(chemo)therapy treatment and added on demand during radiotherapy, will improve patients' nutritional status, tolerability to the radio(chemo)therapy, quality of life, and other clinical outcomes compared to commencement of oral nutritional supplements during the course of irradiation treatment. There are two cohorts in this trial, cohort 1 included patients with oral nutritional supplements and cohort 2 included patients with tube feeding (nasogastric tube or percutaneous endoscopic gastrostomy).

This clinical trial will be conducted in a single-center, prospective, and randomized manner. In this protocol, the standard radio(chemo)therapy duration is 6-7 weeks. Early enteral nutrition intervention (EEN) refers to starting enteral nutrition intervention 2 weeks before post-operative radio(chemo)therapy begins and stopping this intervention when post-operative radio(chemo)therapy completes. Standard enteral nutrition intervention (SEN) refers to starting of enteral nutrition intervention on demand during (chemo)radiotherapy. Nutritional supplementation was given either through the oral route (Cohort 1) or tube feeding (nasogastric tube or percutaneous endoscopic gastrostomy, cohort 2). Dietitians will design meal plans for both groups of subjects so that their normal diets will provide 25-30 kcal/d/kg body weight in addition to nutritional supplements.

Inclusion criteria

• Subject is male or female, between 18 and 70 years old;
• Subject has clinical or radiological diagnosis of oral cancer (stage III and stage IV), had surgical resection 3 or 4 weeks prior to radio (chemo)therapy, and plans to receive radio (chemo)therapy treatment;
• Subject has Karnofsky Performance Score (KPS) ≥ 60 and an expected life expectancy ≥ 6 months;
• Subject is willing to comply with the study protocol, able and willing to consume study product according to the protocol;
• Subject has voluntarily signed and dated the informed consent form (ICF), approved by an Institutional Review Board (IRB) / Independent Ethics Committee (IEC) prior to any participation in the study

Exclusion criteria

• Except for oral cancer and oropharyngeal cancer, subject has malignant tumors or serious infectious diseases, such as tuberculosis activity, respiratory system, cardiovascular system, urinary system diseases, systemic edema and ascites caused by diseases, etc., cannot participant in study in the opinion of study physician.
• Subject has dysfunction of liver, kidney or gallbladder, cannot participant in study in the opinion of study physician.
• Subject has gastrointestinal diseases to cannot tolerate enteral nutrition (such as intestinal bleeding, intestinal obstruction, severe digestive malabsorption, severe nausea and vomiting and diarrhea) that preclude his or her participation in the opinion of study physician;
• Subject has diabetes
• Subject has known history of allergy or intolerance to any ingredient in the investigational product;
• Female subjects are pregnant or plan to get pregnant within a year or are postpartum and non-lactating;
• Subject has mental illness, cannot understand ICF, unwilling to provide informed consent.
• Subject has amputation or implanted electronic devices or metal, it may be inappropriate to use BIA to measure body composition
• Subject is currently or has participated in any clinical trial 2 months prior to enrollment.
• Subject plans to take nutritional supplements and/or traditional Chinese medicine regularly during study in the opinion of study physician. Multi-vitamin and multi-mineral supplements are exception.