This is a fistula. it is an opening that develops between the area of the cancer site and the outside of the body. Detritus from the damage done to the tissues and body fluids are discharged from the body via this opening. You don't say much about his previous issues, but I would assume that he, in one previous fights, had radiation and therefore is not getting it this time. You also do not mention if he has recently had surgery to remove as much of the cancer as possible. In a third bout with this disease, the weapons/tools we have against it are fairly limited, and those are surgery and chemo. Chemo as a monotherapy, is usually not considered curative in nature in oral/head and neck cancers, but palliative. So depending on what they have had done, (surgery perhaps) this fistula and discharge are a by product of those procedures. That they comment that they are waiting on the chemo to start working makes me believe that they have not approached removal of al the cancer by some sort of salvage surgery. More information would allow us to be more helpful, as in this post I am doing a lot of educated guessing. It goes without saying that all of us here wish for him the best possible outcome from this situation.