Good Morning and welcome! I am Dr. Loretta, a licensed veterinarian and I am happy to answer your question.
I am so sorry to hear about Chino's terrible condition...I know how devastating this can be and you only want what is best for your precious guy.
This is a terrible cancer because it is so invasive and cannot be removed due to its position. Radiation treatment will slow down the growth of this mass and give Chino a longer good quality of life as apposed to you not doing anything. It does not have the bad side effects that it does in humans and will help Chino be pain free for a longer period of time.
I also say this because it appears that, since Chino is not showing any serous signs yet, that he is in one of teh first stages and this is where teh radiation will do the most good.
Check out this LINK....http://www.petmd.com/blogs/fullyvetted/2012/aug/nasal_tumors_slow_and_insidious_killers-26882
this may help with this terrible decision that you will have to make for yoru precious Chino.
Again, I know this is very hard on you and Chino and I know you will do what is best for your precious guy.
Does that make sense to you?
Please let me know if you have ANY other questions. My goal is to give you 100% satisfaction and if you are not yet satisfied, please REPLY so I can clarify for you.
Sincerely, XXXXX XXXXX