Not often discussed, but a valuable measure of prostate cancer bone activity is serum (in the blood) alkaline phosphatase. It is a normal enzyme produced naturally by the body. Everyone produces some of this enzyme regardless of his or her state of health, gender, or age.

The tissues that produce the most alkaline phosphatase are the bones and liver.  When prostate cancer spreads to the bones, its most common target, the cancer breaks down the bones and leaks alkaline phosphatase into the blood where it can be measured by a simple and inexpensive blood test.

Measuring the levels of alkaline phosphatase in your blood provides insight into the levels of cancer bone activity caused by the prostate cancer.

There is some evidence that men with high levels of alkaline phosphatase, shorter time to PSA Nadir post-treatment and pain were associated with an increased risk of progression to castrate resistance.