Hello Marie-Lyne,

I had a peg tube inserted before my surgery for ssc of the right tonsil. I was at 145 lbs. pre-cancer and dropped to 121 lbs. in two weeks after the surgery. When I started using the peg on a reguler bases I gained most of the weight back in about 6 weeks. It is a personal decision on your part. He will lose weight during treatment. How much would be a guess. Some have swallowing problems which doesn't allow enough nutrition to be taken in orally to heal and maintain weight.
Some go without the peg and do fine. If he can eat enough to heal and maintain his weight the better off he will be. Thats just my opinion. The old saying "Use it or Lose it comes in to play here.
Go to the search engine at the top of the page and type in PEG, You will have enough to read for quite some time.

All My Best, Danny Boy