Hi, Thanks for writing in. Please see that your grand father gets 1800 kcal food energy daily and most of this might be given as fluids and a nasogastric tube might have to be inserted for better acceptance and energy utilization. Generalized weakness might be due to malnutrition and combined vitamin and mineral deficiency. His general condition requires to be improved and this can be done by providing him minimum daily nutritional and fluid requirements. You can include protein and vitamin supplements to give him extra energy. Unfortunately the life expectancy in stage 4 cancer prostate is between 6 months to two years. Please encourage him to eat and drink fluids regularly. Give him maximum support and care. Please do not worry.