My dad has spine metastes frm primary prostate cancer, terminal, indefinate hormone therapy...whats average prognosis please?

Still some options: I assume he has failed hormonal treatments. If his age and physical condition permits, there are some options. The oral hormone pill zytiga (abiraterone acetate) and chemotherapy (if a candidate then taxotere usually) can be considered. For the spine metastases radiatin can be very helpful in pain control. Average survival is widely variable after hormones have failed can vary and is in the range of 18-20 months.

Depends how long: How long on hormones? If just started the cancer may respond for average of several years. If he was already on hormones for long time prognosis is worse months to a year or two using other option such as different drugs or chemotherapy. Not cureable at this point just delaying progression. Some are offering Provenge (sipuleucel-t) but it's new and not known how effective, this is a vaccine type of therapy.

Mets prostate cancer: The 2 year survival of the average person with bone mets is 40%. This may range from 6 months to 10years depending on the aggressiveness of the cancer (high gleason score:8, 9, or10). Intermittent therapy is sometimes used depending on initial response. Talk to the urologist or oncologist for what is right for your dad.