Barb,
I know it is hard to understand.. ??  You do not smoke so I understand your thoughts. ( I am guessing)
I first had tongue cancer and thought after surgery all was well...  I guested Wrong!!!  I did quite smoking for 6 months.,  Then started again...  Then had cancer spread to other nodes.  
OK, now you ask, why did I smoke.??  I did because I did not know that the cancer had already spread.  I did because this is my addiction for over 40 years.  I started smoking when I was 13.  I am smoke free as of 2005 and I am very proud of it!!
Now here is a new lesson for you.  You do not have to be a smoker to get this type of cancer.  Shocking !! isn't it??  I was very shock to learn this.
When I was diagnosed with this, I thought well it is your own fault.!!  Then I learned later that people that did not smoke got it...  So now what??
I hope this will help you understand what is what.  Smoking is a addiction, a chemical, a drug.  Even coffee is considered the same.  So it is important for all of us to learn everything we can about CANCER.
Take care and keep Learning!!
Diane