Osteoporosis in Women with Cancer

What is osteoporosis?

If you have osteoporosis, your bones become porous and weak. As they lose strength, they are more likely to break. People with osteoporosis are particularly at risk for breaking these bones:

• Spine

• Hip

• Wrist

• Pelvis

• Upper arm

If you have osteopenia, you also have bone loss, but not as much as with osteoporosis. People with osteopenia are more likely to develop osteoporosis if something is not done to stop the bone loss.

Cancer and some of its treatments can increase your risk for osteoporosis.

How does osteoporosis develop?

Bone is made of calcium and other minerals, which make it hard. Bone density refers to the mineral content of the bones. It is related to how hard and strong bones are. Low bone density is a trait of osteoporosis.

Like other tissues in the body, bone constantly repairs and renews itself. This process is called remodeling. Two kinds of cells carry out remodeling in bone:

• Osteoclasts. Cells that break down (resorb) bone. They also release calcium into the blood.

• Osteoblasts. Cells that create new bone. They also draw calcium from the blood.

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

In young people, bones lengthen and increase in density. After about age 35, however, a person's bones start to lose density and strength. Most cases of osteoporosis result from the quicker bone loss, which occurs for any of these reasons:

• Decrease in hormone (estrogen and testosterone) levels 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. During menopause, estrogen production in a woman's ovaries greatly slows down. This hormone 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. If you don't take measures to prevent or slow bone loss, osteoporosis can occur.

In men, bone loss generally begins later. And it advances more slowly than it does in women. Men tend to have larger and stronger bones than women do. Plus, they do not go through the abrupt hormonal changes that occur with menopause. Still, as men age, they do lose 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?

Certain cancer treatments can increase the risk for osteoporosis for both men and women. Some chemotherapy drugs used for breast cancer can cause a loss of bone density. Certain hormone therapies for breast and prostate cancer can, too. A number of strategies can help prevent and treat osteoporosis. Talk about these options with your health care team.

What causes osteoporosis in women with breast cancer?

If you have breast cancer, you may be at higher risk for osteoporosis than other women. Here are some of the reasons why:

• Early Menopause. Certain chemotherapy treatments used for breast cancer can cause the ovaries to stop making estrogen. That brings on menopause. Early menopause may also result when the ovaries are removed (oophorectomy). Or it can occur if you have radiation to your ovaries. These procedures are done to slow breast cancer growth because estrogen can cause some breast tumors to grow. However, the sudden lowering of estrogen levels also causes rapid bone loss.

• Chemotherapy. Some chemotherapy drugs may cause a loss of bone density.

• Hormone Therapies. In some breast cancers, the hormones estrogen and progesterone can speed up tumor growth. Hormone therapies are used to prevent this from happening, but can speed up bone loss, too. Hormone therapy may include ovary ablation or taking medications, such aromatase inhibitors:

  • Ovarian Ablation. The inactivation of the ovaries can occur with surgery to take out the ovaries, or it can occur when the ovaries are treated with radiation. Ovarian ablation can also be done with drugs called luteinizing hormone-releasing hormone (LHRH) analogs, such as goserelin (Zoladex) or leuprolide (Lupron). For women who have not reached menopause, this can immediately bring about menopause and rapid bone loss. This is sometimes done in premenopausal women to decrease their breast cancer risk, or in women with breast cancer whose tumors grow in response to estrogen. It is also done in women with ovarian cancer.

  • Aromatase inhibitors, such as Arimidex (anastrozole) and Femara (letrozole). These drugs are used to treat postmenopausal women with breast cancer. These drugs are known to lead to a loss of bone density.

Can osteoporosis be prevented or treated in women with breast cancer?

Have you had breast cancer and gone through menopause, either naturally or as a result of treatment? If so, you should consider having routine screenings for bone loss. A type of X-ray called the bone mineral density test is safe and noninvasive. It can do all these things:

• Diagnose osteoporosis

• Detect low bone density

• Monitor the effectiveness of treatments

• Predict the risk for future fractures

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

Lifestyle changes you can make

Here are some lifestyle approaches you can take to prevent bone loss:

• Get plenty of calcium and vitamin D. Calcium comes from the food we eat. Good sources include dairy products, such as milk, yogurt, and cheese. Some nondairy foods are also good sources, such as salmon, spinach, and tofu. Vitamin D comes from diet and the sun. The recommended daily intake of calcium is 1,000 mg for young to middle-aged adults and 1,200 mg for women older than age 50. The recommended daily dose of vitamin D is 600 international units (IU) daily and 800 IUs for women older than 70.

• Exercise. Regular physical activity can help prevent bone loss. Weight-bearing exercises are particularly helpful. These include jogging, dancing, and stair-climbing.

• Stop smoking. Smoking causes a loss of bone density.

• Limit alcohol intake. Have no more than one drink a day.

Prescription drugs that may help

Here are some medical approaches you can use for preventing and treating bone loss:

• Bisphosphonates. These drugs prevent the breakdown of bone. The FDA has approved Actonel (risedronate), Boniva (ibandronate), Reclast (zoledronic acid), and Fosamax (alendronate) for preventing and treating osteoporosis.

• Calcitonin. This is a naturally occurring hormone important for calcium regulation and bone metabolism. Miacalcin (calcitonin) is usually taken as a nasal spray.

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

• Selective estrogen receptor modulators. The FDA has approved Evista (raloxifene) for the prevention and treatment of osteoporosis. It can also be used to reduce the risk of breast cancer in women who are at higher risk. If you've had breast cancer, discuss the use of raloxifene carefully with your medical oncologist. Researchers are continuing to learn about its effects on cancer and its interactions with other cancer treatments. 

Talk with your doctor to see if there are other treatments you should consider.