It all depends on a number of factors. If you're mouth, throat, eating, chewing ability is already compromised by surgery, which may effect your your nutritional status during treatment, other co-morbidities you may have, if already underweight or close to it, lose 5% of your body weight unintetionally, are malnourished, doctors feel you won't follow instructions on adequate nutrition, hydration during treatment, mental status, the dosage of radiation, where radiated, bilaterally or ipsilateral, and if having chemoradiation or radiation alone, your preference, your doctor's opinion, all factor in to get one or not.

I didn't have a peg during induction chemo, but due to the severe consequence of it, a peg was put in, and lost 110lbs. Actually, I don't even remember them putting it in I was that bad. I kept my peg, and for other treatments I still lost 40, 10, and recently 5 lbs, and used it to supplement my diet, although I'm peg reliant anymore, I'm not take it out since it can be a life saver, and was mine for a while. I had me 4 years now, and can eat everything. As far as losing your swallowing ability, you need to exercise your mouth, dry swallow, and the tongue, throat muscles have memory, like all muscles, so you get it back quickly. Losing your swallowing ability probably has more to do with surgery, and radiation depending on the dosage, where radiated, especially the BOT area, which is intracal in swallowing.