Breast Cancer and Bone Density: What You Need to Know

A researcher explains the impact certain treatments may have on bone health

There’s a lot to consider about your health while undergoing treatment for breast cancer. But while fertility and hair preservation tends to get the most attention, bone health can also be impacted by breast cancer treatments.

Breast cancer itself doesn’t usually reduce bone density, which is a term used to describe the amount of minerals contained in a certain volume of bone. Low bone density is linked to a higher risk of developing osteoporosis. However, breast cancer treatments that lower estrogen may increase the risk of bone loss. 

Below, a Breast Cancer Research Foundation researcher explains why this happens, how doctors monitor bone health during treatment, and the latest approaches to protecting your bones in general. 

How Does Breast Cancer Affect Bone Density?

Breast cancer itself doesn’t typically weaken bones. However, “there are a few treatments for breast cancer that can reduce bone density,” says Norah Lynn Henry, MD, PhD, breast cancer research professor in the Division of Hematology/Oncology at University of Michigan Rogel Cancer Center.

These treatments usually lower estrogen, which helps to maintain healthy bones, Dr. Henry explains. This reduction in estrogen can speed up bone loss over time. As a result, bone health has become an important part of breast cancer care. 

Why Breast Cancer Treatment Can Increase Bone Loss

Lifetime estrogen exposure can increase the risk of estrogen-dependent breast cancers. To stop tumor growth, breast cancer treatments target estrogen. Since bone health depends on estrogen, lowering it can increase bone loss, as explained in what you need to know about hormone therapy and breast cancer. “Estrogen is necessary for maintaining bone density,” Dr. Henry says. 

But different breast cancer treatments may impact bone health in different ways. 

Aromatase Inhibitors and Bone Density

Aromatase inhibitors are typically used to treat hormone receptor-positive breast cancer in postmenopausal women. These inhibit the aromatase enzyme, which converts androgens like testosterone into small amounts of estrogen. 

But as Dr. Henry stresses, this can impact bone thickness since estrogen is critical to maintain bone density. And because aromatase inhibitors are linked with bone mineral  loss which decreases bone density, and increases the chance of osteoporosis and fractures, doctors will typically monitor bone health as part of treatment. 

Early Menopause and Ovarian Suppression

In premenopausal women, the ovaries are the main source of estrogen, and reducing estrogen levels through ovarian suppression methods can slow estrogen-dependent tumor growth. It can be accomplished with agents that decrease estrogen production by the ovaries (GnRH agonists) or with bilateral oophorectomy. But lowering the body’s estrogen production may cause these patients to enter menopause early and may accelerate bone loss, Dr. Henry says. “This is also why women who go through natural menopause have a decrease in bone density over time,” she says. 

Younger patients, in particular, may be affected because the drop in estrogen can be sudden and sharp. 

Chemotherapy and Bone Health

Chemotherapy may impact bone health in a few ways. It can damage the ovaries, leading to ovarian failure or a  decrease in the ovary’s production of estrogen which interferes with bone density over time. 

“Chemotherapy can also have a direct effect on bone cells, also causing bone loss that often does not reverse after chemotherapy ends,” Dr. Henry says. 

Osteopenia, Osteoporosis, and Breast Cancer

Breast cancer treatment may raise the risk of developing several conditions linked to lower bone density, including osteopenia and osteoporosis. 

Osteopenia refers to lower-than-normal bone density that doesn’t meet the diagnostic threshold for osteoporosis, a bone disease that develops when bone mineral density and bone mass decreases, or when the structure and strength of bone changes. Osteoporosis is linked to a higher risk of fractures. 

Breast cancer treatment can lower the body’s production of estrogen and impact bone density, but it can also directly impact bone cells, leading to bone loss. 

Monitoring Bone Density During Breast Cancer Treatment

Healthcare teams monitor bone health in a few ways during breast cancer treatment. One is with a dual-energy X-ray absorptiometry (DEXA) scan, an X-ray that measures the thickness and strength of bones. This is usually measured in the hip and the spine. 

“It is recommended that bone density be monitored with DEXA scans at baseline and then every two years while taking aromatase inhibitor therapy or in patients who experience premature menopause,” Dr. Henry says. A DEXA scan is different from a mammogram, which is used to detect breast cancer. A mammogram and bone density measurements through DEXA scans are very different. 

Your healthcare provider may also check vitamin D levels periodically to make sure your levels are sufficient, according to Dr. Henry. Vitamin D helps to regulate the absorption of calcium in the gut, a mineral that hardens and strengthens bone.

Protecting Bone Health During and After Treatment

Many people can take proactive steps to maintain healthy bones during and after breast cancer treatment. Dr. Henry recommends:

• Doing weight-bearing exercise. This triggers bone-building cells called osteoblasts to make new tissue, creating denser, stronger bones.
• Avoiding smoking. Smoking causes an imbalance in bone turnover, leading to lower bone mass. 
• Minimizing alcohol. Heavy alcohol use suppresses the activity of osteoblasts, which can lower bone mass. 
• Eating a bone-strengthening diet. Henry suggests having “sufficient” calcium and vitamin D, ideally through your diet, to strengthen bones. 

Exercise and Strength Training

Light weight-baring exercise, resistance training, and staying physically active can support bone density by triggering osteoblasts to make new tissue. If you’re able, try to follow the Physical Activity Guidelines for Americans’ recommended 150 minutes or more of moderate-intensity exercise a week, along with two days of muscle-strengthening activity a week. Your  healthcare team can provide personalized guidance on exercise.

Nutrition for Healthy Bones

A balanced diet is important for your overall health, including bone health. For healthy bones, Dr. Henry says it’s important to make sure you get in enough calcium and vitamin D a day. Most adults, women and men, need 1,000 milligrams (1,200 milligrams if you are over 51) of calcium a day and 15 micrograms of vitamin D daily.

“However it can be difficult to consume enough vitamin D through the diet so when levels are low, we will often recommend that patients take a supplement,” Henry says. 

Medications That Help Protect Bone Density

If your bone density is low or declining, your healthcare provider may suggest that you take certain medications to protect your bone density, Henry says. Those may include:

• Bisphosphonates. These medications improve bone mineral density and may be taken orally or administered intravenously. . 
• Denosumab. This medication is given  every six months by injection. It strengthens bones and prevents fractures by blocking a protein called RANKL that breaks down bone tissue. 
• Newer bone-building therapies. Bone-building treatments–medications that stimulate new bone formation, supplements like calcium and vitamin D, and lifestyle strategies such as strength training and a nutrient-rich diet–stimulate bone growth while supporting existing bone density. 

Research Is Improving Bone Health After Breast Cancer

Scientists continue to try to support bone health during and after breast cancer. “We have always focused on both trying to reduce risk of breast cancer recurrence as well as trying to limit negative effects of therapy, including the negative impact of cancer treatments on bone health,” Dr. Henry says. 

Because some cancer treatments can impact bone loss, many healthcare providers are intervening early to prevent bone loss vs. a more traditional approach of watching and waiting. Scientists have also developed newer medications to build bone rather than simply slowing bone loss. 

Many people go on to live long, healthy lives after breast cancer, which is why researchers continue working on treatment plans to help patients maintain their quality of life. The Breast Cancer Research Foundation is committed to supporting research that improves survivorship and long-term health.

Looking After Your Bone Health

Bone loss is a recognized side effect of some breast cancer treatments. However, many healthcare providers engage in early monitoring of bone density and intervention to preserve bone health during these treatments. 

Ongoing research supported by the Breast Cancer Research Foundation continues to improve survivorship and quality of life.

Support the research behind these lifesaving discoveries. Donate, start a fundraiser, or explore other ways to give and help fund the science that’s moving breast cancer research forward.

Frequently Asked Questions

Can breast cancer treatment cause osteoporosis?

Some breast cancer treatments may interfere with bone density, which can raise the risk of osteoporosis. Those include aromatase inhibitors,  GnRH agonists, ovarian suppression, chemotherapy, and more. Speak to your oncologist about your bone health concerns during your breast cancer treatment to explore your options to support your bone density. 

Does everyone taking aromatase inhibitors lose bone density?

No. “Not everyone loses bone density when they take aromatase inhibitors,” Dr. Henry says. “The same factors that lead to increased bone density in females in general, such as younger age, obesity, and [being Black] also seem to be protective for bone loss during aromatase inhibitor therapy.”

Can bone loss caused by breast cancer treatment be prevented?

Sometimes. There are many options to preserve and support bone health during breast cancer treatment, including lifestyle factors, a diet rich in vitamin D and calcium, and medications, if needed. If you have concerns about your bone health during breast cancer treatment, talk to your healthcare provider about your options.