What is the longevity with prostate bone cancer?

Do you mean prostate cancer that has spread to the bone? Or survival rates for prostate cancer versus bone cancer?

In the case of the former, I believe the prognosis is bad. The highest 10 year survival rates (http://longevity.about.com/od/longevityandillness/a/prostate_le.htm) for prostate treatment is a prostatectomy (surgical prostate removal), but if the cancer has already spread to the bone then prostate removal will not solve the problem, because the cancer has already metastasized.

In the case of the latter, there are different Demographics and different subtypes of cancer to compare! This, combined with different treatment options, dramatically affects the survival rate.