Bone Loss

What is bone loss?

Bone loss is a weakening of the bones that may be caused by aging, cancer, or cancer treatment. Bone loss may be diagnosed when the results of a test called a bone scan indicate weak bones. However, many individuals do not realize they have bone loss until they experience a fracture. Treatment for bone loss may consist of surgery to repair a fracture, radiation to treat cancer in the bones, or drug therapy, including the newer bisphosphonate drugs, which can also prevent bone loss.

Bone loss occurs when there is decreased calcification or reduced density of the bones. The result is weak bones that are at increased risk of fracture. Bone loss can occur as part of the normal aging process or as a complication of cancer or cancer treatment.

What causes bone loss?

Normal bone is constantly being broken down and rebuilt, a process called remodeling. Every week, humans recycle 5 percent to 7 percent of their bone mass. Bone loss occurs when there is a disruption to this process. Bone loss may occur as a result of:

• Osteoporosis - a weakening of the bones related to aging and other factors
• Hormonal therapy - for the treatment of breast and prostate cancer
• Chemotherapy - for the treatment of cancer in women
• Bone cancer or bone metastases - cancer that has spread to the bones

Does cancer treatment contribute to bone loss?

Some cancer treatments can increase bone loss. Hormonal therapies administered in the treatment of breast and prostate cancer can leave patients more susceptible to bone loss. Treatment with chemotherapy may also lead to bone loss in some patients.

Patients that are diagnosed with early stage breast or prostate cancer often receive long-term treatment with hormonal therapy. The goal of hormonal therapy is to reduce the levels estrogen in women and androgens (male sex hormones) in men, since these hormones can stimulate the growth of breast and prostate cancers. However, these hormones also play an important role in maintaining healthy bones, and reducing their levels may cause bone loss.

What are the signs and symptoms of bone loss?

Bone loss is sometimes called a “silent disease” because it occurs without symptoms. People may not know they have bone loss or low-density bones until they become so weak that a sudden strain, bump, or fall causes a fracture. Fractures can occur in any bone. However, fractures of the hip or spine are particularly troublesome and are often a sign of bone loss. When these bones are healthy, they can withstand significant impact; however, when an individual has low bone density, even a minor fall may result in a fracture.

How is bone loss diagnosed?

Bone loss is diagnosed with a bone density scan called  dual energy x-ray absorptiometry (DEXA). DEXA scanning is the most widely used method for measuring bone mineral density. Bone density or bone loss is calculated from the amount of energy that travels through the bone and is picked up by the detector. The minerals in bone, predominantly calcium, weaken the transmission of the x-rays through the bone. The more dense the bone is, the fewer x-rays get through to the detector. The use of two different x-ray energy sources greatly improves the precision and accuracy of the measurement.

How can bone loss be prevented?

Bisphosphonate drugs can effectively prevent loss of bone that occurs from metastatic lesions, reduce the risk of fractures, and decrease pain. Bisphosphonate drugs that are FDA approved for the treatment of cancer-related skeletal complications include Zometa® (zoledronic acid) and Aredia® (pamidronate). Of these two drugs, Zometa appears to demonstrate the strongest activity. An added benefit of Zometa is that it is administered in a dose ten times lower than Aredia, which considerably reduces the administration time from several hours to 15 minutes, resulting in a more convenient regimen for patients.

How can osteoporosis be treated and/or prevented?

Osteoporosis is a weakening of the bones related to aging and other factors. Although there is no cure for osteoporosis, a number of medications have been approved by the FDA to prevent and/or treat osteoporosis in postmenopausal women. You should consult with your physician for the most appropriate medication.