Boy thats a tough one. I have started eating a lot heathier the last year. Thinking back I started taking some Virgin Coconut Oil in the spring for about a week and I've had less problems with biting my lip/cheek. Two weeks ago I bit my lip so hard while eating my wife heard the crunch, it didn't turn into a cancer sore it just hurt for a couple days.
I also take Dr. Schulze superfood and IF#1 on a infrequent basis since this spring and plan on using it on a much more regular basis.
From what I've read and found to be true myself I believe Cancer sores are pretty much A PH thing, I can't say this as a fact but it's what it seems to be for me.