Pelvic Bone/Bladder Involvement

Hello,
My Dad is dealing with advanced prostate ca, which has invaded his pelvic bone and bladder. He has had one procedure to remove growth in bladder, and surgeon says he needs another ( last one was 2 months ago!). Also, his pelvic bone, is causing such pain. Dr has suggested time-released opiate medication. My Dad is reluctant to take pain meds, afraid of mental acuity. Does anyone have information or experience with pain meds for such severe pain? Also, I know the bladder problem is severe, showing the ca is spreading to other organs - Dr. said in a younger man, they would remove it, but my Dad is 77 and a heart patient, the surgery would be too serious at this time. There is talk of a catheter to spine area, to give him meds that way - if needed - feeling that is a more direct way to give pain meds.
Just looking for any ideas to give him comfort or hope. Thanks for any input, I have gained a lot of information and support from you folks! Thank-you.