Bone Health During Cancer Treatment

Why Cancer Treatment Affects Bones

Bone is living tissue that is constantly broken down and rebuilt. Oestrogen in women and testosterone (much of which is converted to oestrogen) in men keep that balance steady. When hormone levels drop sharply, bone is broken down faster than it is replaced, and bone mineral density falls. Over time this can lead to osteopenia (low bone mass) and osteoporosis, where bones become fragile enough to break after a minor fall, or even without one, typically in the spine, hip or wrist.

Cancer-treatment-related bone loss is often faster than the gradual loss that comes with normal ageing or menopause, which is why guidelines recommend checking and protecting bone health early rather than waiting for a fracture.

Treatments That Cause Bone Loss

General risk factors add to this: older age, a previous fragility fracture, a parent who broke a hip, low body weight, smoking, more than about two alcoholic drinks a day, low activity, and conditions such as rheumatoid arthritis. See our hormone therapy guide for more on the treatments themselves.

DEXA Scans and Fracture Risk

A DEXA (or DXA, dual-energy X-ray absorptiometry) scan measures bone density at the hip and spine. You lie on a padded table for a few minutes while a scanner arm passes over you. It is painless and the radiation dose is very low.

Understanding your T-score

• −1.0 and above: normal bone density
• Between −1.0 and −2.5: osteopenia (low bone mass)
• −2.5 or below: osteoporosis

Doctors also estimate your 10-year fracture risk with tools such as FRAX, which combine the scan with age and other risk factors. Treatment decisions are based on overall risk, not the T-score alone.

When to be scanned

ASCO guidance for people with non-metastatic cancer recommends a baseline DEXA scan for those at increased risk of osteoporosis, including anyone starting an aromatase inhibitor, ADT or ovarian suppression, with repeat scans about every 2 years, or more often if bone density is falling or medicines are started. Ask whether you have had a baseline scan if you are starting one of these treatments.

Calcium, Vitamin D and Lifestyle

• Calcium: most adults need a total of about 1,000 to 1,200 mg a day. Get as much as possible from food (dairy, fortified plant milks and cereals, tofu set with calcium, tinned fish with bones, leafy greens) and use supplements only to fill the gap; very high supplement doses do not add benefit.
• Vitamin D: needed to absorb calcium. Many people are advised to take 800 to 1,000 IU a day, especially in winter or with little sun exposure. Your team may check your blood level, particularly before starting a bone medicine.
• Stop smoking and keep alcohol within recommended limits.
• Prevent falls: check your eyesight, remove trip hazards, use night lights, and ask about medicines that cause dizziness. Neuropathy in the feet increases fall risk.
• Protein and body weight: eat enough protein and avoid unintentional weight loss, which both weaken bones and muscles.

Exercise

Exercise is recommended for nearly everyone during and after cancer treatment. For bones, the most helpful types are:

• Weight-bearing activity: brisk walking, hiking, stair climbing, dancing or tennis, most days of the week
• Resistance (strength) training: weights, resistance bands or body-weight exercises, at least two days a week, gradually increasing
• Balance training: tai chi, yoga or simple balance exercises, which lower the risk of falls

Bone-Strengthening Medicines

If your fracture risk is high, for example because of osteoporosis on DEXA, a previous fragility fracture, or a high FRAX score, your team will usually recommend a bone-modifying medicine in addition to calcium, vitamin D and exercise.

Evidence in cancer patients

• Aromatase inhibitors: bisphosphonates prevent much of the bone loss, and in the ABCSG-18 trial denosumab every 6 months reduced clinical fractures in postmenopausal women taking aromatase inhibitors.
• ADT for prostate cancer: denosumab reduced new spinal fractures in men on ADT in a large trial, and bisphosphonates maintain bone density.
• Adjuvant bisphosphonates in early breast cancer: separately from bone protection, guidance from ASCO and Ontario Health suggests considering zoledronic acid (or clodronate where available) for postmenopausal women with early breast cancer who are candidates for systemic treatment, because a large overview of trials found it modestly reduced recurrence in bone and breast cancer deaths. A common schedule is zoledronic acid every 6 months for 3 years.

Osteonecrosis of the Jaw and Other Risks

Osteonecrosis of the jaw (ONJ) is an uncommon but important side effect of bisphosphonates and denosumab, in which a patch of jawbone becomes exposed and does not heal. It is rare at the doses used to protect bones against treatment-related loss, and more frequent with the higher, monthly doses used for bone metastases, especially over longer periods. Most cases follow a tooth extraction, dental infection or poorly fitting dentures.

Other possible effects

• Atypical thigh-bone fractures: rare, mainly after several years of treatment; report new aching in the thigh or groin
• Low blood calcium: particularly with denosumab and in people with kidney problems or low vitamin D
• Kidney effects: with intravenous bisphosphonates, so kidney function is checked before doses
• Acute-phase reaction: short-lived fever and aches after a first zoledronic acid infusion

Bone Metastases

Some cancers, especially breast, prostate, lung, kidney and thyroid cancers and multiple myeloma, can spread to or start in the bones. Bone metastases can cause pain, fractures, raised blood calcium and, if in the spine, pressure on the spinal cord.

• Bone-modifying agents at higher doses: zoledronic acid (typically every 3 to 12 weeks) or denosumab 120 mg (Xgeva, every 4 weeks) reduce fractures and other skeletal complications. The ONJ precautions above are especially important at these doses.
• Radiotherapy: often a single treatment or short course, effective for painful bone metastases. See radiation therapy.
• Surgery: to stabilise bones at high risk of breaking, or to relieve pressure on the spinal cord.
• Treating the cancer itself: hormone therapy, chemotherapy, targeted therapy or immunotherapy; radium-223 is used for some prostate cancers that have spread to bone.
• Pain control and supportive care: see cancer pain and palliative care.

Frequently Asked Questions

Which cancer treatments cause bone loss?

The biggest causes are treatments that lower sex hormones: aromatase inhibitors (letrozole, anastrozole, exemestane) for breast cancer, androgen deprivation therapy (ADT) for prostate cancer, ovarian suppression, and chemotherapy that brings on early menopause. Long courses of steroids, stem cell transplant, some stomach and bowel surgery, and high-dose thyroid hormone after thyroid cancer can also thin bones.

Do I need a DEXA scan during cancer treatment?

If your treatment is likely to cause bone loss, yes. ASCO guidance recommends a baseline bone density (DEXA) scan for people at increased risk, including those starting an aromatase inhibitor, ADT or ovarian suppression, and repeating it about every 2 years, or sooner if results or risk change. The scan is quick and painless and uses a very low dose of X-rays.

If I take letrozole, do I need bone infusions?

Not necessarily. Many people on letrozole only need calcium and vitamin D (preferably from food first), regular weight-bearing exercise and DEXA monitoring. A bone-strengthening medicine, either a tablet such as alendronate, a zoledronic acid infusion or a denosumab injection, is recommended if you have osteoporosis, a fragility fracture or a high calculated fracture risk. Separately, some postmenopausal women with early breast cancer are offered zoledronic acid infusions because they also modestly reduce the risk of the cancer returning in bone.

Can bone density improve after stopping an aromatase inhibitor?

Often partly, yes. Studies have shown that bone density tends to stabilise and may partially recover after aromatase inhibitors are stopped, particularly in the spine. Recovery varies between people, so a follow-up DEXA scan and continued exercise, calcium and vitamin D are still worthwhile. If you are on denosumab, do not stop it without a plan, because bone loss can rebound quickly.

How much calcium and vitamin D should I take?

For most adults, guidelines suggest a total of about 1,000 to 1,200 mg of calcium a day, ideally mostly from food such as dairy, fortified plant milks, tinned fish with bones and leafy greens, with supplements only to make up the gap. Vitamin D needs vary; many people are advised to take 800 to 1,000 IU daily, and your team may check your blood level. Very high doses are not better and can be harmful, so check with your team before taking large supplements.

What is osteonecrosis of the jaw?

Osteonecrosis of the jaw (ONJ) is a rare condition in which an area of jawbone is exposed and heals poorly, usually after a tooth extraction or dental infection. It is linked to bisphosphonates and denosumab, mainly at the higher, more frequent doses used for bone metastases. Having a dental check-up before starting, keeping up good oral hygiene and telling your dentist about your treatment reduce the risk. Report jaw pain, loose teeth, swelling or exposed bone in the mouth.

What is the difference between bisphosphonates and denosumab?

Both slow down the cells that break bone down. Bisphosphonates (such as alendronate tablets or zoledronic acid infusions) bind to bone and their effect lasts for some time after stopping. Denosumab is an injection under the skin every 6 months for treatment-related bone loss (or monthly at a higher dose for bone metastases); it works quickly but wears off quickly, so stopping it suddenly can cause rapid bone loss and spinal fractures unless another treatment follows. Choice depends on kidney function, ability to take tablets correctly, dental health and preference.

What exercise is best for bone health?

A mix of weight-bearing activity (brisk walking, stair climbing, dancing), progressive resistance training with weights or bands two or more days a week, and balance exercises to prevent falls. If you have bone metastases or osteoporosis in the spine, ask for advice from a physiotherapist or exercise professional familiar with cancer before lifting heavy weights or doing high-impact or twisting exercises.

Is bone pain during cancer treatment a sign of bone metastases?

Not usually. Aromatase inhibitors commonly cause joint and muscle aches, filgrastim injections can cause bone pain, and arthritis is common. However, new pain that is persistent, worse at night, localised to one spot or getting steadily worse should be reported so your team can decide whether a scan is needed. Back pain with leg weakness, numbness or new bladder or bowel problems needs emergency assessment.

Related Resources

• Letrozole (Femara)
• Anastrozole (Arimidex)
• Exemestane (Aromasin)
• Tamoxifen (Nolvadex)
• Hormone Therapy for Cancer
• Hot Flashes
• Breast Cancer
• Prostate Cancer

References

1. Shapiro CL, et al. Management of Osteoporosis in Survivors of Adult Cancers With Nonmetastatic Disease: ASCO Clinical Practice Guideline. J Clin Oncol. 2019;37(31):2916-2946.
2. Eisen A, et al. Use of Adjuvant Bisphosphonates and Other Bone-Modifying Agents in Breast Cancer: ASCO-OH (CCO) Guideline Update. J Clin Oncol. 2022;40(7):787-800.
3. Early Breast Cancer Trialists' Collaborative Group (EBCTCG). Adjuvant bisphosphonate treatment in early breast cancer: meta-analyses of individual patient data from randomised trials. Lancet. 2015;386(10001):1353-1361.
4. Gnant M, et al. Adjuvant denosumab in breast cancer (ABCSG-18): a multicentre, randomised, double-blind, placebo-controlled trial. Lancet. 2015;386(9992):433-443.
5. Smith MR, et al. Denosumab in men receiving androgen-deprivation therapy for prostate cancer. N Engl J Med. 2009;361(8):745-755.
6. National Comprehensive Cancer Network (NCCN). NCCN Clinical Practice Guidelines in Oncology: Survivorship; Breast Cancer; Prostate Cancer.
7. National Cancer Institute. Hormone Therapy for Breast Cancer; Hormone Therapy for Prostate Cancer. cancer.gov.
8. U.S. Food and Drug Administration. Prescribing information for Prolia and Xgeva (denosumab), Reclast and Zometa (zoledronic acid).
9. Van Poznak C, et al. Role of Bone-Modifying Agents in Metastatic Breast Cancer: ASCO-CCO Guideline Update. J Clin Oncol. 2017;35(35):3978-3986.