Hi, Thanks for writing in. Vomiting is a common side effect of cancer treatment. It is possible that he received radiation therapy to his neck region and this caused fibrosis of the thoracic part of esophagus which is located behind the vocal cord. The esophageal radiation fibrosis might cause strictures which cause discomfort in eating and drinking fluids. The patient might also have pain and difficulty in swallowing. It is suggested that an investigation like barium swallow is done to know if the food pipe has developed any stricture. Then attempts might be made to widen the stricture area and allow the passage of food and liquids. To keep him hydrated, he might be encouraged to take fluids containing proteins and electrolytes in small amounts regularly. If stricture is persistent then regular IV fluids and nasogastric tube might be required to keep him hydrated and prevent malnutrition. Please do not worry.