Your bones support your body, give it shape, and help you move. Your bones also help protect your heart, lungs, and brain. Even though your bones feel hard and rigid, they are living tissues that constantly rebuild themselves during your life. During your childhood and teenage years, your body adds new bone faster than it gets rid of old bone. After about age 30, you can start to lose bone faster than your body makes it, which can weaken the bones and increase the risk of breakage. Some bone loss is natural as men and women age, but women are at higher risk of significant bone loss. Throughout your adult life, it’s important to take steps to make sure you don't lose too much bone and put yourself at risk of easily breaking a bone by falling or tripping.
This becomes even more critical after menopause. When you go through menopause, your levels of estrogen and other hormones drop sharply. Because estrogen helps maintain bone density, this drop can lead to significant bone loss and, over time, to low bone density.
Doctors typically use two different words to talk about low bone density:
- Osteopenia means you have lower-than-normal bone density. Osteopenia isn't a disease, but it can mean that you're at higher risk for breaking a bone.
- Osteoporosis is a disease and means that your bone density is so low that your bones are brittle and can break easily. White and Asian women are at highest risk for osteoporosis, but all women and men older than 50 are at risk for the disease.
Breast Cancer Treatments and Bone Loss
Many breast cancer treatments increase the risk of bone loss by lowering estrogen levels in the body. If you’re premenopausal when you’re diagnosed with breast cancer, the following treatments can accelerate bone loss:
- Certain types of chemotherapy that cause either temporary or permanent menopause
- Medications known as luteinizing hormone-releasing hormone (LHRH) agonists, which shut down the ovaries’ production of estrogen temporarily or permanently in some cases
- Surgical removal of the ovaries, which is recommended for some women
- The hormonal therapy tamoxifen, which blocks the effects of estrogen in cells throughout the body and, as a result, can interfere with bone density in premenopausal women
- If you’re diagnosed with hormone-receptor-positive breast cancer after menopause, you might be prescribed aromatase inhibitors (AIs) that can cause bone loss. These include Arimidex (chemical name: anastrozole), Aromasin (chemical name: exemestane), and Femara (chemical name: letrozole). AIs stop the production of estrogen in your body. The main sources of estrogen in postmenopausal women are the adrenal glands and fat tissue, not the ovaries. If you’re postmenopausal and take tamoxifen, on the other hand, it actually can help build bone density. For postmenopausal women, tamoxifen’s effects on bone is similar to the effects of the estrogen you used to have in your body naturally.
Tests for Bone Health
The good news is that osteopenia and osteoporosis don’t develop overnight. During perimenopause, you can start to lose some bone mass, but the risk of significantly decreased bone density is greatest right before and several years after menopause. After that, the rate of bone loss tends to level off.
You and your doctor can work together to monitor your bone health and take action if you’re losing bone density. Bone density (or bone mineral density) is a measurement of how strong your bones are. The higher the density, the stronger and healthier your bones are.
There are several tools your doctor can use to check your bone health, including a physical exam; blood and urine tests to measure your calcium levels; and bone density tests. These tests use x-rays or sound waves to measure how strong your bones are. Bone density tests are used to definitively diagnose bone loss and osteoporosis.
The most widely recognized bone mineral density test is dual-energy x-ray absorptiometry, commonly known as a DEXA scan. Your doctor may recommend having a baseline DEXA scan as you begin treatment and, depending on the results, perhaps every year or two afterwards. A DEXA scan uses low levels of x-rays and is quick and painless. A scanner passes over your whole body while you're lying on a cushioned table. A DEXA scan can measure the bone mineral density of your whole skeleton as well as specific points that are more likely to break, such as the hip, spine, and wrist. Using a DEXA scan to measure bone mineral density at the hip and spine is considered the most reliable way to diagnose osteoporosis and predict the risk of breaking a bone.
Many experts also recommend using the Fracture Risk Assessment Tool, or FRAX, an online questionnaire developed by the World Health Organization to assess your 10-year probability of a hip fracture or other bone fracture due to osteoporosis. You can ask your doctor about FRAX if he or she doesn’t mention it. (If you’ve already taken bone-strengthening bisphosphonate therapy—see below—then the FRAX tool would not be for you.)
Prevention and Treatment Strategies
When it comes to bone loss, prevention truly is your best defense. Whether testing shows any evidence of bone loss or not, the following strategies can help keep your bones strong:
- Calcium at 1,200 mg/day, taken through a combination of diet and supplements. Good sources of calcium include:
- Low-fat dairy products such as milk, cheese, and yogurt
- Foods such as leafy green vegetables, almonds, and beans
- Calcium-fortified foods such as fruit juices and cereals (check the label)
- Vitamin D at 800-1,000 IU/day or more. Multivitamins typically include 400 IU, so you may need an additional supplement.
- Quitting smoking
- Weight-bearing exercises that help strengthen bones
- Maintaining a healthy body weight
- Limiting alcohol use
If bone density testing shows that you have worsening osteopenia or osteoporosis, your doctor may recommend you take a bisphosphonate. Bisphosphonates interfere with the activity of bone cells known as osteoclasts, which reabsorb bone tissue (in contrast to osteoblasts, which create it). This helps to reduce bone turnover and boost bone density. Common examples include Fosamax (alendronate sodium); Actonel (chemical name: risedronate); Boniva (chemical name: ibandronate); and Zometa and Reclast (chemical name: zoledronic acid).
Besides bisphosphonates, other medications that may be used to treat osteoporosis in women who’ve had breast cancer include:
- Evista (chemical name: raloxifene): Evista is a selective estrogen response modifier (SERM) that can be used to treat osteoporosis in post-menopausal women.
- Prolia (chemical name: denosumab): Prolia helps stop the development of cells that are responsible for removing old bone. As a result, the rate of bone loss slows.
Duavee (chemical name: conjugated estrogen/bazedoxifene) is another medication you might hear about; Duavee reduces hot flashes and reduces the risk of osteoporosis in postmenopausal women. But Duavee contains hormones, so it is not recommended for women with a history of, or high risk for, breast cancer.
Your primary healthcare provider can help you make decisions about treatment or refer you to a bone specialist. For more information on bone loss, osteoporosis and ways to keep your bones strong, visit Bone Health in the Day-to-Day Matters section and Osteoporosis in the Treatment Side Effects section.