that's too bad. They can redo the surgery to loosen things up at a later date and time - I don't believe in nevers - My surgeon used a fairly large flap on my tongue and has offered to reduce the size if i want. It fits okay it's not super huge, so I'm fine for now. He calls it debulking surgery. So chances are your son's incision can be adjusted later ideally take care of the cancer first then when he's healed and cancer free work on the mechanics of returning his life to a normal state. I know someone else who had the sutured area loosened. (apparently they'd stitched her whole tongue to the floor of her mouth!)

It does sound to me a little like your dr is not on top of his game. go through with rads and chemo and then later on when he goes to have the surgery adjusted - perhaps push for different surgeon. Though I would make a point of telling him what is wrong with your son's function now.

hope this helps. He likely needs you to advocate for him.

hugs.