Some treatments for breast cancer can affect your bones, which can increase your risk of developing osteoporosis in the future.

The following information explains what osteoporosis is, why treatments such as chemotherapy, tamoxifen or aromatase inhibitors could increase your risk, and how you can help protect your bones with simple lifestyle changes.

Read more information about looking after your bones, including how healthy eating and physical activity can help keep your bones strong and healthy.

What is osteoperosis? 

Osteoporosis is a condition where your bones lose their strength and become fragile and more likely to break (fracture).

Bones have a thick outer shell and a strong inner mesh filled with collagen (protein), calcium salts and other minerals. The inside looks like a honeycomb, with blood vessels and bone marrow in the spaces between struts of bone.

Osteoporosis means some of these struts of bone become thin (and can disappear altogether) and can fracture easily with little or no force.

Osteoporosis causes no general pain or symptoms, so often a person won’t realise they have the condition until a fracture happens. The most common sites for a fracture to occur are the wrist, hip and back (spine).

Although osteoporosis cannot be cured, treatments are available to try to keep the bones strong and less likely to break.

What causes osteoperosis? 

Our bones increase in density and strength until we reach our late 20s. Around the age of 35, we start to lose bone density as part of the natural ageing process. This happens gradually over time. A large reduction in bone density is known as osteoporosis. About half the population will have osteoporosis by the age of 75.

The hormone oestrogen protects against bone loss and helps to maintain bone density and strength. Women who have gone through the menopause are at increased risk of osteoporosis and fractures because their ovaries no longer produce oestrogen (low levels of oestrogen are still produced in body fat).

Risk factors

Factors that increase the risk of osteoporosis include:

  • increasing age (women and men)
  • low levels of the hormone oestrogen because of:
  • an early (before the age of 45) natural menopause or hysterectomy with removal of the ovaries
  • treatment for cancer (such as chemotherapy, hormone therapy and ovarian ablation or suppression
  • the eating disorder anorexia nervosa
  • a family history of osteoporosis or hip fracture
  • previous wrist, spine or hip fracture resulting from little or no trauma
  • long-term use of corticosteroid tablets (for conditions such as arthritis and asthma)
  • medical conditions that affect the absorption of foods, such as Crohn’s disease, coeliac disease or ulcerative colitis
  • conditions that leave you immobile for a long time
  • low body weight
  • regularly drinking more than the recommended amount of alcohol
  • smoking
  • a diet that is low in calcium and vitamin D (calcium can help to maintain bone density)

Breast cancer treatment and bone health

Some breast cancer treatments can increase the risk of osteoporosis. Both women who haven’t yet gone through the menopause (pre-menopausal) and women who have gone through the menopause (post-menopausal) may have an increased risk of osteoporosis related to breast cancer treatment.

Chemotherapy

Chemotherapy can affect the function of the ovaries, causing an early menopause in some women. This means less oestrogen is produced which can reduce bone density.

Women aged 45 or under whose periods have stopped for at least a year as a result of treatment may also be at risk of osteoporosis, even if their periods restart.

Some research has shown that post-menopausal women who have chemotherapy may notice greater loss of bone density than they would have had without chemotherapy.

Ovarian suppression

Ovarian suppression is when the ovaries are removed, or temporarily or permanently stopped from working. This means there’s less oestrogen in the body to stimulate the cancer to grow, which can also reduce bone density. Ovarian suppression can be done using a type of hormone therapy, surgery or radiotherapy.

Tamoxifen

Tamoxifen can be given to both pre-menopausal and post-menopausal women. It blocks the effect of oestrogen which helps stop breast cancer cells from growing.

In pre-menopausal women, taking tamoxifen may cause a slight reduction in bone density. This is unlikely to lead to osteoporosis unless ovarian suppression is given as well. However, your risk may be higher if you’re 45 or under and your periods have stopped for at least a year.

In post-menopausal women, taking tamoxifen slows down bone loss and can reduce the risk of osteoporosis.

Aromatase inhibitors

Aromatase inhibitors (including anastrozole, letrozole and exemestane) are mainly used to treat breast cancer in post-menopausal women. These drugs reduce the amount of oestrogen circulating in the body, which can reduce bone density.

Some pre-menopausal women have an aromatase inhibitor at the same time as ovarian suppression. Having these two treatments can reduce bone density.

The likelihood of developing osteoporosis while taking aromatase inhibitors also depends on how healthy your bones were before your breast cancer treatment.

How is oseoperosis diagnosed?

Generally osteoporosis is diagnosed using a bone density scan, often referred to as a DEXA (dual energy x-ray absorptiometry) or DXA scan.

A DEXA scan is used to measure bone mineral density (BMD). BMD is the amount of calcium and other minerals in an area of bone and is a measurement of bone strength. The lower your bone mineral density, the more likely osteoporosis will be diagnosed.

A DEXA scan uses a very small amount of radiation, and is quick and painless. While you’re lying down, an x-ray scanner will pass over your body taking pictures of your lower spine and hips.

Your results will include a T-score. The T-score measures how your BMD compares to a (reference) range of young healthy adults with average BMD.

  • T score above -1 is normal.
  • T score between -1 and -2.5 is classified as osteopenia (low bone density).
  • T score below -2.5 is defined as osteoporosis.

If your scan result shows you have osteopenia you will be given advice about changes you can make to your lifestyle, such as diet and exercise. You won’t usually need treatment, but your doctor will discuss this with you.

When assessing your osteoporosis risk, your doctor may also use an online fracture risk assessment tool such as FRAX or Qfracture to predict your risk of fracture over a period of time and help decide if you need treatment. Research has shown that bone fragility can be assessed more accurately by including other risk factors, such as your age, family history of hip fracture or whether you have had a fracture in the past.

You can read more about having a DEXA scan, the FRAX and Qfracture online assessment tools on the National Osteoporosis Society website.

Do I need a DEXA scan?

The National Institute for Health and Care Excellence (NICE) – an independent organisation responsible for providing national guidance on promoting good health and preventing and treating ill health – recommends that women at risk of developing osteoporosis should have their bone mineral density (BMD) assessed.

If your specialist team has a concern about your risk of developing osteoporosis they may suggest a bone mineral density scan to check your bone health before you start treatment.

NICE guidance

NICE recommends that people with early invasive breast cancer should have a DEXA scan to assess bone mineral density if they:

  • are starting aromatase inhibitor treatment
  • have treatment-induced menopause
  • are starting ovarian suppression therapy.

Follow-up DEXA scans may be recommended every two years for some people.

Keeping bones healthy

There are several ways to keep your bones strong and healthy with simple lifestyle changes.

Find out more about looking after your bones.

Treatment for osteoporosis

Osteoporosis cannot be cured, but treatments are available to try to stop the bones getting any weaker and to make them less likely to fracture.

Osteoporosis in people who have had breast cancer is most commonly treated with a group of drugs called bisphosphonates. Bisphosphonates help strengthen your bones and reduce your risk of fractures. Bisphosphonates may also be prescribed to protect your bones if you’re taking an aromatase inhibitor (exemestane, letrozole or anastrozole).

Denosumab is a drug that may be recommended to prevent fractures. It is given as an injection twice a year and slows the process of bone loss in osteoporosis. It’s a treatment for post-menopausal women who are unable to take certain bisphosphonates and who have particular risk factors for fracture.

You should see your dentist for a check-up before starting treatment and tell them that you are being treated with bisphosphonates or denosumab, particularly if you’re due to have any dental work. 

Strontium ranelate is another drug that may occasionally be used to treat severe osteoporosis in post-menopausal women. It is taken as granules dissolved in water. Like denosumab, it can only be prescribed in certain circumstances, such as in people who are at high risk of fracture.

If you are found to have osteoporosis, you will be advised about appropriate drug treatment and its possible side effects. You will also be given guidance on any changes to your diet or lifestyle that may be helpful.

The National Osteoporosis Society has more information on these drugs on its website.

Bisphosphonates and denosumab are also used to treat breast cancer that has spread to the bones (secondary breast cancer in the bone). This is not the same as having osteoporosis. 

Last reviewed: January 2016
Next planned review begins 2018

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