If Dad has been offered surgery, it would seem his diagnosis is such that he would be treated with cureable intent. If this does not entirely kill all his cancer cells, RT may do so, perhaps in conjunction with Hormone treatment or he could go straight to RT. Severity and range of side effects can vary but most men would prefer the side effect risk rather than do nothing and risk the rotten death of PCa that can be a possibility. A lot can come down to life expectancy of the patient. 63 is quite young and an average man could expect twenty or more years but untreated PCa with shorten this. It often becomes the case regardless of PCa that as a man ages he can't perform as well as he once did. You slow down, react more slowly and need medical help to optimise what you have and can do. You might need to wear glasses, have dentures, use a walking stick, take pills to help regulate, need pads and or other things. You do go to the dentist, optician, GP or whoever. It makes sense to accept help and this is true for PCa too. The only reason I can think of for not doing anything is for men that only expect to have a short time left to them or have had enough of life. Suggest you tell Dad he is valued and you want him to be cured if possible so he can be about for many years even with a few side effects. You don't want him to face the possibility of an earlier and painful death if treatment might stop or defer this.