My father has a T3 N0 M0...locally invasive castration resistant prostate cancer. He has no symptoms, lives independently, and is generally physically well. He was referred only last week to oncology who have suggested radiotherapy...6 fractions over 6 weeks...so not aggressive. The advice we received was that this is likely to provide good local control. He would have to travel 30 miles to the local specialist centre. Side effects were discussed. 

After no discussion with me or anyone else he has decided not to go ahead...and would very likely refuse any other treatment. I know that of course he has an absolute right to do this, but I fear that he has rushed to a decision, he will not give me a cogent reason why he has refused...only that it is his decision he will not engage in any discussion. I don't want to force him to do anything he does not want, and want to support him as best I can. But I do want him to make an informed descision. 

How can I best address this?