Some treatments for breast cancer can increase your risk of getting osteoporosis, a condition that affects the bones.
The following information explains what osteoporosis is, how treatment for breast cancer may increase your risk, and how it’s diagnosed and treated.
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 osteoporosis?
Our bones are made of a thick outer shell and strong inner mesh. 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 become thin or snap and the bones then become fragile and can break (fracture) with little or no force.
Osteoporosis can’t be cured, but treatments are available to try to keep bones strong and less likely to break.
What causes osteoporosis?
Around the age of 35, bone loss increases as part of the ageing process, which can itself lead to osteoporosis. About half the population will have osteoporosis by the age of 75.
The female hormone oestrogen protects against bone loss and helps maintain bone density and strength.
Women who have gone through the menopause (post-menopausal) are at increased risk of osteoporosis because their ovaries no longer produce oestrogen (low levels of oestrogen are still produced in body fat).
Some breast cancer treatments can cause an early menopause, increasing the risk of osteoporosis. Other treatments can reduce the amount of oestrogen circulating in the body.
Breast cancer treatment and bone health
Women who haven’t gone through the menopause (pre-menopausal) may have an increased risk of developing osteoporosis due to the treatment they are given. This includes:
Women who have gone through the menopause (post-menopausal) may be at increased risk of developing osteoporosis if they take an aromatase inhibitor as part of their treatment.
Chemotherapy can affect the function of the ovaries, causing an early menopause in some women. This means less oestrogen is produced which can lead to a reduction in bone density.
Ovarian suppression and ablation
Temporarily or permanently stopping the ovaries from working may be offered as a treatment for breast cancer. This can be done using a type of hormone therapy, surgery or radiotherapy.
This causes a rapid and significant reduction in oestrogen, which can lead to a loss of bone density.
Tamoxifen can be given to both pre-menopausal and post-menopausal women to block the effect of oestrogen on breast cancer cells.
In pre-menopausal women, tamoxifen may cause a slight increase in bone loss, although it’s unlikely to lead to osteoporosis unless treatments to stop the ovaries from working are given as well.
When taken by post-menopausal women, tamoxifen slows down the process of bone loss and can reduce the risk of osteoporosis.
Aromatase inhibitors (including anastrozole, letrozole and exemestane) are used to treat breast cancer in post-menopausal women.
These drugs reduce the amount of oestrogen circulating in the body, which may lead to a reduction in bone density.
However, people with good bone density levels before breast cancer are much less likely to develop osteoporosis while taking an aromatase inhibitor, which is usually taken for up to five years.
How is osteoporosis diagnosed?
Often osteoporosis isn’t found until a fracture happens. The wrist, hip and spine are the sites where fractures most commonly occur.
Bone density scan
Osteoporosis is diagnosed with a bone density scan, often referred to as a DEXA (dual energy x-ray absorptiometry) or DXA scan.
This type of scan can also be done to assess the risk of osteoporosis developing. Other factors, such as your age, family history of osteoporosis or whether you have broken a bone in the past, will also help predict your risk of breaking a bone.
The DEXA scan measures bone mineral density (BMD), a measurement of bone strength. The lower your BMD, the higher your risk of fracture.
The National Institute for Health and Care Excellence (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 ablation or suppression therapy.
Read more about having a DEXA scan on the National Osteoporosis Society website.
If a DEXA scan shows a decrease in bone mineral density that isn’t low enough to be diagnosed as osteoporosis, you may have a condition called osteopenia.
If this happens you’ll 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.
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
Although osteoporosis cannot be cured, treatments are available to try to stop the bones getting any weaker and to make them less likely to fracture.
If you’re found to have osteoporosis, you will be advised about appropriate drug treatment and given guidance on any changes to your diet or lifestyle that may be helpful.
Osteoporosis in people who have had breast cancer is most commonly treated with a group of drugs called bisphosphonates. These drugs may also be prescribed alongside an aromatase inhibitor (exemestane, letrozole or anastrozole) to help protect against its effects on the bones.
For more information on bisphosphonates and other drug treatments for osteoporosis, see the National Osteoporosis Society website.
Content last reviewed August 2013; next planned review 2015