Bone Metastases with Prostate Cancer

Photo by SMC Images / Getty Images
Photo by SMC Images / Getty Images. Photo by SMC Images / Getty Images

Certain characteristics make prostate cancer unique compared to other cancers:

·     Slow growing

·     Highly sensitive to hormone therapy

·     Easily monitored with PSA blood testing

·     Fastidious pattern of spread, often exclusively to bone

When prostate cancer spreads it is almost always characterized by having metastases in the bone. Contrary to popular belief, most bone metastases are painless, though there are exceptions.

  Bone fractures, which are relatively common in other types of cancer, are quite rare with prostate cancer.  This is because the metastases tend to draw calcium into the site of metastases, creating a “sclerotic reaction” that fails to weaken bone like other cancers do.

Bone metastases in their early stages, therefore, do relatively little harm. There is, however, one exception to this rule—metastases in the back that grow out of the vertebral body and start pressing on the spinal cord.  This is a very serious development because pressure on the spinal cord can block the blood supply, in effect severing the cord.  Blockage of the cord can result in permanent paraplegia. 

Prompt diagnosis of spinal cord compression from prostate cancer is therefore essential.  All patients with metastases need to report to their doctors immediately any new symptoms which include:  severe back pain, numbness in the legs or loss of urinary or bowel control.

Cord compression is an emergency that requires the immediate initiation of high doses of cortisone combined with radiation (or sometime surgery).  Delays of more than 24 hours reporting these symptoms can result in permanent leg paralysis.    

When bone metastases are extensive, a progressive in blood counts can occur.

  The bone marrow is the site of production for red cells, white cells and platelets.  A reduction in red cells results in anemia.  Progressive anemia causes tiredness and shortness of breath.  Severe anemia may require blood transfusion or treatment with Aranesp or Procrit, hormones that stimulate the marrow to produce more red cells. 

Moderate lowering of platelet counts, which normally are maintained above 100,000, does not usually create any noticeable effect.  Severe lowering of platelet counts, say down to less than 10,000, can cause bleeding.  Platelets are essential for the normal blood clotting process.  Very low levels of platelets are treated with platelet transfusions.

Low white blood counts can in theory result in an increased susceptibility to infections. Problems from low white counts can be counteracted with an injectable hormone called Neulasta.  Neulasta is also used to counteract low white counts caused by chemotherapy. If an infection occurs due to a low white count, antibiotics are of course administered routinely.     

Recent research indicates that men with bone metastases who never had Lupron have improved survival with the early initiation of Taxotere. Additional pharmacological agents that are beneficial for men with bone metastasis are Zometa and Xgeva.

These agents strengthen the bone, reduce pain, counteract osteoporosis and reducing the rate of cancer spread.

Beam radiation directed at painful areas of bone metastases is extremely effective at controlling pain. Spot radiation controls pain very effectively. However, radiation to bone should be used judiciously because radiation permanently kills bone marrow, increasing the risk of further lowering of blood counts. Radiation is occasionally recommended to prevent future bone fractures. However, bone fractures from prostate cancer are uncommon. For this reason, undergoing bone radiation simply to prevent a fracture is rarely necessary.

Xofigo, an injectable form of radiation, can be effective in reducing pain and seems to have only mild or moderate effects on the marrow. When multiple areas of bone pain exist, Xofigo is a logical form of therapy to consider.  Xofigo travels through the blood and concentrates in the metastases. Xofigo’s anticancer effects are potent and have been shown to prolong survival in men with multiple bone metastases.

Metastatic disease is monitored with scans. Radioactive technetium bone scans have been the standard bone scanning method for years. More recently, Fluoride PET bone scans have demonstrated better accuracy. MRI is another accurate scanning technique for evaluating bone.

“Bone metastases” are so common, the term is almost synonymous with “advanced prostate cancer.”  Prostate cancer in the bone usually responds to all the typical anticancer hormonal, immunologic and chemotherapeutic agents commonly prescribed for prostate cancer. When prostate cancer is advanced, the number one priority is to control the metastases. If the metastases are controlled, the disease is controlled.  

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