Maybe Cigarettes do cause Oral Cancer ..BUT ..it can be caused by other things,I do not know what,but I know two people who have had Oral Cancer and been very succesfully treated .
The first a male,had quite a large part of his mouth ( upper palate) removed and replaced with a prothsisis.. his first op was 7 years ago and he is ,as far as I know still in remission.
The second ,a lady ,has recently had an op for Oral Cancer ,i do not know the details as she is only an aquaintance,but it was succesful and she is now recovering.
As far as I am aware neither of these people have ever smoked !!