PSA and Tumor Markers for Prostate Bone Metastasis?

314>This message pertains to the utility of Prostate Specific Antigen (PSA), for the treatment of Advanced Prostate Cancer.





PSA writes Dr. John Lee (Harmone Balance for Men) is produced both within the Prostate Gland and the Breast Tissue. He further writes that the normal cells produce PSA, an anti angiogenesis defence when there are abnormally growing cells in the prostate. This seems to indicate that the PSA has no correlation with what is happening in the bone and anywhere outside prostate. Is this correct?





There are further questions:





(a) How do we monitor bone metastasis and other situations where the cancer has escaped out of prostate. (non-Bone Scan/MRI options)





(b) Are there other prostate tumor markers that can tell us the tumor loads/tumor activity in non prostate areas such as the bones.





(c) Will Acid Phosphatase levels inform us the status of prostate metastasis on bone.





(d) Are Osteoblastic/Osteocystic/Osteocytic rates right parameters to track.





Sam
Reply:There are a few misconceptions here.





* PSA is manufactured almost exclusively by prostate cells. Although there are a few other cell types that can make minute quantities of it, their contribution is so small that PSA is indeed, for all practical purposes, a prostate-_specific_ marker.


However, that doesn%26#039;t mean it measures only cells that reside in the prostate gland.





* In a person with normal prostatic health, prostate cells reside only in the prostate gland. But in a person with advanced prostate cancer, most of his prostate cells have traveled to areas outside the prostate, typically the bones and lungs.








Therefore, for men with advanced prostate cancer, PSA is normally the single best way of tracking the cancer, since it correlates so well with the number of prostate cells in the body -- both within the gland (if it%26#039;s still there) and outside the gland, and thus presumably cancerous.





(a) To specifically find bone metastases, one would normally use an imaging technique, such as a bone scan, a CT scan, and/or a PET scan (preferably one that uses 11C-choline rather than 18F-FDG). It%26#039;s unclear why someone would try to monitor bone metastasis without any attempt to image the bones, so I don%26#039;t know what prompts the question. (Not all imaging techniques use radioactive tracers, for example. And if expense is an issue, then maybe consider simple X-rays.)





(b) There are indeed other tumor markers, but none of them are specific to rogue prostate cells that are in the _bones_, as opposed to rogue prostate cells generally. Such tumor markers include: PSMA, PAP, NSE, CGA, and CEA.





(c) Yes and no. PAP (prostatic acid phosphatase) is useful as a tumor marker, but no tumor marker, so far as I know, can possibly differentiate betwee bone and non-bone metastasis.





(d) Yes and no. If you%26#039;re focusing only on the bone, then you are interested in overall rates of bone-building (osteoblastic) and bone-resorption (osteoclastic) activity. But you won%26#039;t know _where_ the activity is occurring.





Most importantly: In a person has advanced prostate cancer, bone issues are one of the consequences. But it%26#039;s much more important to tend to the cancer itself than to focus on only one of its consequences. If a car is heading downhill and its brakes are failing, one of the consequences will be tiretread left on the roadway. Rather than trying to measure and track the tiretread, it%26#039;s more important to find a turnoff, or a soft ditch, or (best) an alternate braking system.





Good luck!


(BTW, I%26#039;m now also a member of the PCa tribe.)