my brother has had throat cancer twice, he's being through treatment both times, the first being half his tongue removed and his jaw and arears disected, he now has being diagnosed again , what is the prognosis

That's something only your brother's doctor can speak to and even then, the doctor is just making an educated guess.
What was suggested to me in a similar situation is to just concentrate on living each day as fully as one can. Make plans for the future but live for the moment. Sounds trite but it's good advice for all of us because we just never know what will happen. Be supportive, present and caring - try not to dwell on a prognosis.