Hi
you will find all the answers to your questions by using the search engines attached to the home page of this forum.Once you have read all the information available i would then suggest youcome back with more specific questions.Of course most people here will tell you it ain't cancer until someone says it is,and it is difficult to predict what treatment your sister may need.
For a sore on the tongue we need to know a)is it cancer?,b)is the primary?c)what stage is it?all these factors will decide the treatment plan,and of course make sure she is seen in a comprehensive cancer centre.

good luck

liz