Hi Teamshrink,
We've ended up with thousands of dollars of copays since Jack was diagnosed in January. Insurance policies vary widely and you need to call member services to find out what the specifics of yours is. Since you have a 20% copay I'd also call the billing office of the radiation center and ask them for an estimate of your bill. Tell them why, they should be used to this. I've also set up long term monthly payment plans for a few of these big bills. Cancer is not cheap. Good luck.
Regards JoAnne