Osteoporosis in Men with Cancer

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.

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 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. But after about the age of 35, 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:

• Lower levels of the hormones estrogen and testosterone in the body

• Lack of physical activity

• Too little calcium, vitamin D, or both

• Smoking

• Too much alcohol use

• Certain medicines such as steroids

Osteoporosis is more common in women than in men. This is because during menopause, a woman's ovaries greatly slow down how much estrogen they make. Estrogen is a hormone that keeps the bone-dissolving activity of the osteoclasts in check. After menopause the osteoblasts continue to build bone, but they can't keep up with the speed at which the osteoclasts break it down. 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. They don't go through the sudden hormonal changes that occur with menopause. But as they age men do lose bone density. This is 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 for osteoporosis for both men and women. Some chemotherapy medicines used to treat 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. Discuss these options with your 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. Advanced means the disease that has spread throughout the body. Some doctors may also use it when the disease is diagnosed early, before it has spread beyond the prostate.

Low testosterone levels can slow prostate cancer growth, but 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 for osteoporosis. Androgen-deprivation therapies include:

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

• Luteinizing hormone-releasing hormone (LHRH) analogs, or agonists. Medicines such as leuprolide and goserelin lower testosterone levels in the body.

Another class of hormonal medicines used to treat prostate cancer is the antiandrogen agents. This class includes the medicines bicalutamide.

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 for 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. It is also called DEXA (dual energy X-ray absorptiometry).

Once bone is lost, it can't be completely replaced using current therapies. Although it can't 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. For men older than 50, the recommended daily intake of calcium is 1,000 to 1,200 mg, and of vitamin D, 600 to 800 international units (IU). 

• 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 how much alcohol you drink

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

• Bisphosphonates. Bisphosphonates are medicines that prevent the breakdown of bone. There are different types of bisphosphonates. Some are taken by mouth, and others are given by IV. Two bisphosphonates are pamidronate and zoledronate. They are given as shots. They can be used to treat prostate cancer that has spread to the bones. They may also help prevent osteoporosis in men during androgen-deprivation therapy for prostate cancer. Risedronate and alendronate are approved by the FDA for preventing and treating osteoporosis in men and women. Both medicines are available as oral tablets.

• RANKL (receptor activator of nuclear factor kappa-B ligand) inhibitors. These medicines act in a very similar way to bisphosphonates. Denosumab is approved by the FDA to treat osteoporosis. It is also approved to prevent bone loss caused by hormonal therapy given for the treatment of cancer, if used in combination with calcium and vitamin D supplement. 

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