Nah, there's all kinds of bad effects from radiation. Radiation sickness, radiation poisoning, and radiation burns. If you want a direct demonstration of radiation's effects on organic tissue, refer to your local microwave.
It'd be funny to simplify it all down to radiation = cancer, but unless you can find a way to turn that into instant mayhem within the time constraints of a brikwars battle, I have to reject it.
Brikwars tends to ignore both, though. My completely unclear point is that although physically impossible things are extremely common in Brikwars, it seems pointless to come up with rules for things that are physically possible, and then make them do something completely different from what they can do in real life.
I'm going to be honest, I'm not sure if this post makes any sense at all.