Guard Against Osteoporosis When On Androgen-Deprivation (Hormonal) Therapy.

I recently learned of a good friend who has asymptomatic but metastatic prostate cancer which was being controlled by intermittent androgen deprivation (hormonal) therapy. One of the potential side effects of such therapy is the risk of osteopenia and the more serious condition, osteoporosis. Osteoporosis and the processes involved in breaking down bone (resorption) by cells called osteoclasts and generating new bone from osteoblasts are described clearly and briefly in the April 6th, 2013 issue of the Johns Hopkins Hospital Health Alerts. Patients on hormonal therapy are advised to have annual bone density tests known as dexa scans wherein bone density is measured in the lumbar spine and the hip femoral neck. Such patients also usually take bisphosphonates such as Boniva or Fosamax among others to minimize the bone depletion which often accompanies hormonal therapy. Since bisphosphonates also have some potential side effects coinciding with their long term use, my friend was advised not to take bisphosphonates (specifically Boniva) for a year and observe any effect on his bone density. After one year, the dexa scan showed a dramatic and very significant reduction in his bone density especially in the lumbar spine. He was then placed on a relatively new medication called Prolia (formerly called denosumab) which had been approved in 2011 by the U.S. Food and Drug Administration for use in prostate cancer patients whose cancer had not yet metastasized to bone in addition to other cancer patients. 

Prolia works differently from the class of bisphosphonates such as Boniva by specifically binding to RANKL, a transmembrane or soluble protein essential for the formation, function, and survival of osteoclasts, the cells responsible for bone resorption. Prolia thereby prevents RANKL from activating its receptor, RANK, on the surface of osteoclasts and their precursors. Prevention of this RANKL/RANK interaction thereby inhibits osteoclast formation, function, and survival, thereby decreasing bone resorption and increasing bone mass and strength. Prolia is administered as a 6-month. sub-cutaneous injection.

The moral of this anecdote is that prostate cancer patients undergoing androgen deprivation (hormonal) therapy need to consistently monitor and maintain their bone densities using appropriate medications such as bisphosphonates or Prolia and should also engage in regular exercise regimens to maintain bone strength.

 

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