Bone Health After Breast Cancer: Protecting Your Bones During and After Treatment

Why breast cancer treatment can affect your bones

The hormone oestrogen does more than affect periods and fertility. It also helps keep your bones strong by slowing down the natural loss of old bone. When the amount of oestrogen in your body drops, bones can thin more quickly. This is why some breast cancer treatments, which work by lowering oestrogen or switching it off, can affect bone strength over time.

If bones become thinner than normal but not yet at a level called osteoporosis, this is known as osteopenia. If they thin further and become more fragile, this is osteoporosis, which raises the chance of a bone breaking (a fracture). This guide explains why this happens after breast cancer, how it is checked, and the many things that help protect your bones. It is general health information, not personal medical advice. Your breast care team, oncologist and GP know your situation, so always talk to them about your own bone health and any worries.

Which treatments raise the risk, and why

Not everyone treated for breast cancer is at higher risk of bone thinning. It depends mainly on which treatments you have and whether you have been through the menopause. According to Breast Cancer Now and Cancer Research UK, the main reasons bones can thin after breast cancer are:

• Aromatase inhibitors. These tablets (anastrozole, letrozole and exemestane) are used by women who have been through the menopause. They lower oestrogen to very low levels, which can speed up bone loss and raise the risk of fractures.
• An early or treatment-induced menopause. Chemotherapy can damage the ovaries and bring on the menopause early. Some women also have treatment to switch off the ovaries (ovarian suppression). Both lower oestrogen and can affect bone strength, sometimes in younger women whose bones would otherwise have stayed strong for years.
• Aromatase inhibitors plus ovarian suppression in younger women. Cancer Research UK and Breast Cancer Now note that using these together causes a bigger drop in bone density, so bone health is watched especially closely.

Tamoxifen, another common hormone therapy, works differently. Breast Cancer Now explains that in women who have been through the menopause, tamoxifen can actually slow bone loss and may help protect bones. In women who have not yet been through the menopause, Breast Cancer Now says tamoxifen may slightly increase the risk of bone thinning, though this is unlikely to lead to osteoporosis unless it is combined with treatment to switch off the ovaries. So being on hormone therapy does not automatically mean your bones are at risk; the type of treatment matters a great deal.

Some other things can add to the risk, whether or not you have had cancer. These include getting older, a family history of osteoporosis, smoking, drinking a lot of alcohol, having a low body weight, and long-term use of steroid tablets. Your team takes all of this into account when planning how to look after your bones.

The DEXA scan: checking your bone strength

The main way to check bone strength is a bone density scan, usually called a DEXA or DXA scan (dual energy X-ray absorptiometry). It is quick, painless and uses only a very small amount of radiation. You lie on a flat table while a scanner passes over you, usually measuring the hip and spine. Breast Cancer Now notes the scan itself takes around 20 minutes, and you stay fully clothed.

The scan gives a result called a T-score, which compares your bone density to that of a healthy young adult. As a general guide used in the UK:

• A T-score above -1 is considered normal bone density.
• A T-score between -1 and -2.5 suggests osteopenia (bone density lower than normal, but not osteoporosis).
• A T-score of -2.5 or below suggests osteoporosis.

NICE recommends that women starting an aromatase inhibitor have their bone density assessed, and in practice most people beginning these tablets are offered a DEXA scan around the start of treatment as a baseline. The scan may then be repeated to track any change. Breast Cancer Now notes that follow-up scans are often done after about 2 to 5 years, depending on your first result and your overall risk. If you are on tamoxifen alone after the menopause, you may not need a baseline scan, because tamoxifen tends to protect bones rather than thin them. Your team will explain what is right for you. A scan showing some thinning is not a cause for alarm; it simply helps your team act early to keep your bones strong.

Protecting your bones: diet, exercise and lifestyle

Whatever your scan shows, there is a lot you can do yourself to keep your bones as strong as possible. The NHS and the Royal Osteoporosis Society highlight the same simple steps that help everyone's bones, and they matter even more during breast cancer treatment.

Stay active with the right kind of exercise. Two types of activity help bones most:

• Weight-bearing exercise, where you are on your feet and supporting your own weight, such as walking, climbing stairs, dancing or jogging. The pull on the bones helps keep them strong.
• Muscle-strengthening (resistance) exercise, such as using light weights, resistance bands or doing exercises like gentle squats, which works the muscles that pull on bone.
• Balance exercises, such as tai chi, which help prevent falls. Many fractures happen because of a fall, so steadying your balance protects you too.

Start gently, especially if you are tired from treatment or recovering from surgery, and build up slowly. If you are unsure what is safe for you, ask your team or a physiotherapist, particularly if you have had bone problems or surgery affecting movement.

Get enough calcium and vitamin D. Calcium is the main building block of bone, and vitamin D helps your body absorb it. A balanced diet with calcium-rich foods such as milk, yoghurt, cheese, tinned fish with soft bones, and green leafy vegetables supports bone health. The NHS advises that, because we cannot make enough vitamin D from sunlight in the UK during autumn and winter, adults should consider a daily supplement of 10 micrograms of vitamin D from about October to March, and all year round if you are rarely outdoors. If you are at risk of osteoporosis or taking medicine for it, your doctor may advise a higher dose and a calcium supplement, so check what is right for you rather than starting high-dose supplements on your own.

Look after the rest of your health too:

• Stop smoking. The NHS notes that smoking weakens bones, and stopping is one of the best things you can do for your health overall.
• Keep alcohol within the UK low-risk guideline of no more than 14 units a week, spread over several days, as heavy drinking weakens bones and raises fall risk.
• Try to keep to a healthy weight, as being underweight can make bones more fragile.
• Reduce the risk of falls at home, for example by clearing trip hazards, using good lighting and wearing well-fitting shoes.

Bone-protecting medicines

If your scan shows your bones are thinning, or if you are at higher risk, your team may suggest a bone-strengthening medicine alongside the lifestyle steps above. These are well-established treatments used widely for osteoporosis. Breast Cancer Now and NICE describe the main options:

• Bisphosphonates. These are the most common bone-protecting medicines. They include alendronic acid and risedronate (usually weekly tablets), and zoledronic acid and ibandronic acid (given as a drip or injection). They slow bone loss and lower the risk of fractures.
• Denosumab. This is given as an injection, usually twice a year, and may be offered to women who cannot take bisphosphonates. It is important not to stop denosumab suddenly without medical advice, as bone loss can rebound, so your team will plan this carefully.
• Other options, such as raloxifene or teriparatide, may be considered in particular situations, for example if other treatments are not suitable.

There is an added benefit for some women. NICE and Cancer Research UK note that bisphosphonates such as zoledronic acid are offered to some women who have been through the menopause not only to protect bones, but because they can also reduce the risk of breast cancer coming back, including in the bones. If your team recommends a bisphosphonate, they will explain whether it is mainly for your bones, to lower recurrence risk, or both.

Before and during treatment with these medicines, it is worth keeping up with dental check-ups, because a rare side effect can affect the jaw. Tell your dentist you are taking a bone-protecting drug, and tell your cancer team if you need dental work. Your team will go through the benefits and any side effects with you so you can decide together.

Living well and looking after your bones long term

Bone thinning after breast cancer often causes no symptoms at all, which is exactly why monitoring matters. Many people feel reassured to know that bone health is something their team keeps an eye on, and that there is so much that can be done. Looking after your bones is also part of looking after your whole self after treatment, alongside managing tiredness, staying active and keeping up with your follow-up appointments.

A few simple habits help you stay on top of it:

• Keep your DEXA scan and follow-up appointments, and ask what your results mean for you.
• If you are prescribed a bone-protecting medicine or supplements, take them as advised and mention any side effects rather than stopping on your own.
• Build a little weight-bearing and strengthening exercise into your week, even short, regular sessions count.
• Contact your GP if you have new back pain, lose height, or have a fall, as these can be signs worth checking.

Good information and timely follow-up are not equally easy for everyone to reach. As a charity, we work to improve early detection and access to follow-up care in underserved communities, where bone health and other long-term effects of treatment can too easily be overlooked. Wherever you live, your breast care nurse, oncologist or GP is the right person to guide your own bone health, so please do raise any questions with them.