Osteoporosis and How Is It Related to Hormone Therapy (ADT)?

Osteoporosis is a general loss of bone mass that can lead to fractures. (A related condition, osteopenia refers to bone density that is lower than normal peak density but not low enough to be classified as osteoporosis.)  ADT increases a man’s risk of developing osteopenia or osteoporosis. The longer a man remains on ADT, the greater our risk for loss of bone mass (bone mineral density). (Citation: Michael G. Oefelein, Vincent Ricchuiti, et.aL, J of Urology; Volume 166, Issue 5, Pages 1724-1728 November 2001)

In normal bone, two types of cells called osteoclasts and osteoblasts work together to rebuild and strengthen bone:

  • osteoclasts that destroy old bone
  • osteoblasts that build new bone.

ADT and prostate cancer causes an imbalance between these two cell types resulting in more bone being destroyed than rebuilt, leading to weakening and thinning of the affected bone.

Make sure that you do have a regular bone density test if you are on ADT, no matter the schedule.

This can cause pain and means that the bone can fracture or break more easily.  Men may not even know they have osteoporosis or experience any significant problems with this condition until a fracture occurs. When osteoporosis is present, fractures of the spine are common and may occur while merely bending, lifting, standing, sudden movements, or from other minimal stress. Pain results from the collapse of the small bones of the spine that may have been weakened by osteoporosis. More severe spinal fractures can cause paralysis. Early diagnosis and treatment can prevent these potentially disabling injuries.

How is Osteoporosis Diagnosed?

Early diagnosis is helpful for men on ADT. You can be tested for osteoporosis by having your bone mineral density (BMD) evaluated by a dual energy x-ray absorptiometry (DEXA) scan. DEXA readings can be overly optimistic (i.e., indicate greater BMD than actually exists) because this scan misreads calcification and calcium in the blood vessels close to the bone as being bone itself. DEXA is by far the most common BMD test, but a better scan is a Quantitative Computerized Tomography (QCT). QCT distinguishes vascular calcifications and degenerative joint disease – a common effect of aging on bones – as something different from osteoporosis. (Citation: Smith et al, Cancer 9:2238, 2001). Both scans are safe and painless.

Dexa scans should not be used once there has been a development of confirmed bone metastases.  A man with bone metastases should insist on a QCT scan.

How Is Osteoporosis Treated and Prevented?

  • Stop smoking and reduce drinking alcohol.
  • Taking calcium and vitamin D3.
  • Regular exercise with weight-bearing or resistance exercises.
  • Talk to your doctor about taking an oral (not IV) bisphosphonate.

 

Oral bisphosphonates are commonly used to treat bone thinning (osteoporosis). Bisphosphonates are often given alongside other treatments.

Zoledronic acid (trade name: Zometa), the most commonly prescribed bisphosphonate, targets areas of bone where osteoclast activity is high. It helps bring the balance of osteoclast and osteoblast activity back to normal by reducing the activity of the osteoclasts, in turn reducing pain and helping strengthen the bone. It also means that less calcium will be lost from the bones.  Zoledronic acid is given by a drip (infusion) into the vein through a fine tube called a cannula. It’s usually given in the outpatient department at the hospital. The infusion takes at least 15 minutes and is given every 3-4 weeks.

CAUTION- The experience of many men is that the first infusion of Zoledronic acid must be slowed down to take at least an hour. A too-fast first infusion has been reported to exacerbate the negative side effects, notably “flu-like symptoms.”

Traditional practice has been to give Zometa for as long as it provides a positive outcome.  However, a recent study has cautioned that extended use of Zoledronic acid may in certain cases cause an unusual and serious fracture of the femur bone in the leg. (Citation: http://www.johnshopkinshealthalerts.com/alerts/osteoporosis/Bisphosphonates-for-Osteoporosis_6795-1.html?s=W1R_140125_001&st=email).

A newer bisphosphonate is now available.  The FDA has approved Denosumab, marketed as Xgeva, for men on ADT. It has been shown in clinical trials to increase bone density and prevent fractures in men who develop osteoporosis as a result of androgen deprivation therapy. It has also been shown to delay the onset of bone metastases. Denosumab has been demonstrated to be more effective in reducing bone fractures than zoledronic acid (Zometa).

If your doctor offers you Zometa instead of Xgeva ask him or her why they have made that decision.  Generally, Xgeva is a superior drug, but many oncologists remain loyal to the older standby because of their familiarity with the drug.