Welcome,
I sorry that you have to be here but I'm sure your going to find alot of support here. Your poor Dad truly has been put through alot. I'm so sorry, it's really hard watching the man that gave your comfort your whole life in such a awful way.. This is only my thought but I would talk to other Doctor and see what there feeling are on the risks of radation. My wonderful Dad has Chemo & Radation and the Radation was much worse,they burnt the hell out of his Lungs..
Take care and keep us posted on your Dad!!
Love, Michele