Osteoporosis in Men With Canc... Health Article

Osteoporosis is a disease in which bones become porous and weak. As they lose strength, they are more likely to break. Bones in the spine, hip, wrist, pelvis, and upper arm are particularly at risk of fracture in people with osteoporosis.

Osteopenia is a condition in which less bone has been lost than in osteoporosis. But people with osteopenia are more likely to develop osteoporosis if something is not done to stop the loss of bone.

About 10 million Americans have osteoporosis and 18 million more have osteopenia. The disease usually progresses without symptoms until it is diagnosed after a fracture.

How Does Osteoporosis Develop?

Bone is made up of calcium and other minerals, which make bone hard. Bone density, or more specifically, bone mineral density, refers to the mineral content of the bones. It is related to how hard and strong they are. Low bone density is seen in osteoporosis.

Bone is a type of tissue. Like other tissues in the body, bone constantly repairs and renews itself. In bone, this process is called remodeling. Two kinds of cells carry out remodeling:

• Osteoclasts, cells that break down, or resorb, bone and release calcium into the blood.

• Osteoblasts, cells that draw calcium from the blood and create new bone.

A balance between the bone-building osteoblasts and bone-dissolving osteoclasts keeps bones healthy.

In young people, bones lengthen and increase in density. After about the age of 35, however, bones start to lose density and strength. Most cases of osteoporosis result from the speeding up of bone loss that can occur for a number of reasons:

• Decrease in the levels of hormones (estrogen and testosterone) in the body

• Lack of physical activity

• Lack of calcium and vitamin D

• Smoking

• Excessive alcohol use

• Certain medications.

Osteoporosis is more common in women than in men. This is because during menopause, a woman's ovaries greatly slow their production of estrogen, a hormone that keeps the bone-dissolving activity of the osteoclasts in check. After menopause the osteoblasts continue to build bone, but they cannot keep up with the speed at which the osteoclasts break it down. As a result, a woman begins to lose bone rapidly, especially in the first five years after menopause. If no measures are taken to prevent or slow bone loss, osteoporosis can occur.

Bone loss in men generally begins later and advances more slowly than it does in women. Men tend to have larger and stronger bones than women do and they do not go through the abrupt hormonal changes that occur with menopause. But as they age men do loose bone density, in part because of a natural decrease in testosterone. By age 65 or 70 men and women lose bone mass at similar rates. Calcium absorption, which is needed to keep bones healthy, also decreases in men and women.

How Does Cancer Treatment Affect Bone Loss?

Various cancer treatments can increase the risk of osteoporosis for both men and women. Some chemotherapy drugs used in the treatment of breast cancer and various hormonal therapies for breast and prostate cancer can cause a loss of bone density. There are a number of strategies to prevent and treat osteoporosis. Patients should discuss these options with their healthcare provider.

What Causes Osteoporosis in Men With Prostate Cancer?

It is well known that testosterone and other male hormones, called androgens, can stimulate the growth of prostate cancer. For this reason a common treatment approach for prostate cancer is to lower the level of testosterone in the body. This approach has been successful in treating men with advanced prostate cancer (disease that has spread throughout the body) and it is now used when the disease is diagnosed early, before it has spread beyond the prostate.

While low testosterone levels can slow prostate cancer growth, they can also lead to loss of bone density in men. In particular hormonal therapies that deprive the body of androgens—called androgen-deprivation therapy-- increase the risk of osteoporosis. Androgen-deprivation therapies include:

• Orchiectomy, a surgical procedure to remove the testicles, the main source of testosterone.

• Lutenizing hormone-releasing hormone (LHRH) analogs, or agonists, are drugs that lower testosterone levels in the body.

Another class of hormonal drugs used to treat prostate cancer is the antiandrogen agents. This class includes the drug bicalutamide. It is not clear what effect antiandrogen drugs have on bone density, but there is some evidence that they do not increase the risk of osteoporosis as much as androgen-deprivation therapies do.

Can Osteoporosis in Men With Prostate Cancer be Prevented or Treated?

Not all men develop osteoporosis as a result of androgen-deprivation therapy. But because this hormonal treatment can increase the risk of this disease, these men should consider having routine bone mineral density screenings. A type of X-ray called the bone mineral density test is a safe and noninvasive way to diagnose osteoporosis, detect low bone density, monitor the effectiveness of treatments, and predict the risk for future fractures.

Once bone is lost, it cannot be completely replaced using current therapies. Although it cannot be cured, osteoporosis can be slowed down. A number of approaches are available for preventing and treating osteoporosis in men:

Lifestyle approaches for preventing bone loss in men include:

• Calcium and vitamin D. Calcium comes from the food we eat. Dairy products, such as milk, yogurt, and cheese, and nondairy foods, such as salmon, spinach, and tofu, are good sources. Vitamin D comes from diet and the sun. The recommended daily intake of calcium is 1200 mg and 1500, and of vitamin D, 400 to 800 IU. A higher (greater than 2000 mg/day) intake of calcium has been associated with an increase in prostate cancer risk, but there is no evidence that the recommended dose is associated with progression of the disease.

• Exercise. Regular physical activity, especially weight-bearing exercises such as jogging, dancing, stair-climbing, and arm exercises can help prevent bone loss.

• Stop smoking

• Limit alcohol intake

Medical approaches for preventing and treating bone loss in men include:

• Bisphosphonates. Bisphosphonates are drugs that prevent the breakdown of bone. There are different types of bisphosphonates, some that are taken orally, others that are given intravenously (in a vein). One study to date has shown that a bisphosphonate—pamindronate, which is given as an intravenous injection—can prevent osteoporosis in men during androgen-deprivation therapy for prostate cancer. Other bisphosphonates have not been evaluated in for this purpose, but they are likely to be useful. Risedronate and alendronate are approved by the US Food and Drug Administration (FDA) for preventing and treating osteoporosis in men and women. Both drugs are available as oral tablets. They are well-tolerated and safe. The most common side effects of bisphosponates include diarrhea, abdominal pain, and heartburn. The drug should be taken in the morning with 8 ounces of water at least 30 minutes before eating, and the patient should remain upright during this time to avoid gastrointestinal problems. Another promising bisphosphonate is zoledronate.

• Calcitonin. Calcitonin is a naturally occurring hormone important for calcium regulation and bone metabolism. It is usually given as a nasal spray.