Bone Health and Fractures After Cancer Treatment

NCI names four causes of bone thinning after cancer treatment. They are chemotherapy, steroid medicines, hormonal therapy, and radiation therapy.

For most adults, hormone-blocking treatment is the biggest single driver. It works by stripping out the hormones that keep bone strong. The bone loss is a direct result of the drug doing its job.

Aromatase inhibitors lower estrogen. There are three: anastrozole, letrozole and exemestane. NCI notes they are used mainly in women who have gone through menopause.

Estrogen protects bone. Take it away and bone loss speeds up. MedlinePlus says it plainly about anastrozole. The drug "may cause or worsen osteoporosis. It can decrease the density of your bones and increase the chance of broken bones and fractures."

Joint pain is also a common side effect of these drugs. But aching hands and knees are not the same as bone loss. Sore joints tell you nothing about your bone density. Only a scan does.

Androgen deprivation therapy (ADT) lowers testosterone. NCI lists "loss of bone density" and "bone fractures" among its side effects.

ADT is a family of approaches, not one drug.

• LHRH agonists: leuprolide, goserelin, triptorelin.
• LHRH antagonists: degarelix, relugolix.
• Surgery to remove the testicles, called orchiectomy.

NCI adds a point about time that is easy to miss. "The risk of side effects increases the longer a person is on hormone therapy." Six months of ADT and six years of ADT are not the same bone problem.

Long-term steroids also thin bone. Prednisone and dexamethasone are the common ones. MedlinePlus lists long-term steroid use as a reason to get a bone density test. It names thyroid hormone and aromatase inhibitors in the same sentence.

Radiation matters most where the beam passed through bone. Chemotherapy can push a younger woman into early menopause. That adds estrogen loss on top of everything else.

A DXA scan is a low-dose x-ray. It is also written DEXA. It measures calcium and other minerals in your bones. It usually scans the spine and hip. It is quick and painless.

Results come back as a T-score.

• Normal: minus 1.0 or above.
• Low bone mass, or osteopenia: minus 1.1 to minus 2.4.
• Osteoporosis: minus 2.5 or below.

A T-score compares your bone density with that of a healthy young adult. It applies to women past menopause. It also applies to men aged 50 and over.

Younger women and men under 50 get a Z-score instead. That compares you with people of your own age, sex and ethnicity. Many cancer survivors sit in that younger group. So check which score your report used.

MedlinePlus lists these reasons for a bone density test.

• A history of treatment for prostate cancer or breast cancer.
• Long-term use of steroids, thyroid hormone, or aromatase inhibitors.
• Most women aged 65 and older.
• Younger women, and men of any age, with other risk factors.

Ask for a baseline scan when you start an aromatase inhibitor or ADT. A first scan taken three years in cannot show how much bone you already lost.

Repeat timing depends on that first result. It also depends on your treatment and your other risks. No single interval fits everyone. Ask your team to write the next scan date into your plan. Ask them to name who orders it.

MedlinePlus gives these daily amounts.

• Age 50 and under: 1,000 mg calcium, 400 to 800 IU vitamin D.
• Women 51 to 70: 1,200 mg calcium, 400 to 800 IU vitamin D.
• Men 51 to 70: 1,000 mg calcium, 400 to 800 IU vitamin D.
• Over 70: 1,200 mg calcium, 800 IU vitamin D.

Bring these numbers to your team. Do not act on them alone. Ask them to check the amounts against your own blood results. This matters most if your blood calcium has ever run high.

A bone medicine may be added if bone density is low. MedlinePlus lists these options and how they are given.

• Bisphosphonates: alendronate (Fosamax), ibandronate (Boniva), risedronate (Actonel), and zoledronic acid (Reclast). Pills may be daily, weekly or monthly. The IV form is usually given once or twice a year.
• Denosumab (Prolia): a shot every 6 months.
• Teriparatide (Forteo): a shot under the skin, often daily, given at home.
• Romosozumab (Evenity): a monthly shot under the skin for one year.
• Raloxifene (Evista): taken by mouth.

NCI names two options for men on long-term hormone therapy for prostate cancer. They are bisphosphonates, meaning zoledronic acid or alendronate, and denosumab.

Know the side effects before you start. Bisphosphonate pills can cause heartburn, nausea and belly pain. Rarer but serious problems also occur. These include damage to the jaw bone, an unusual kind of thigh bone fracture, low blood calcium, and a fast, abnormal heartbeat. NCI calls the jaw problem "a rare but serious side effect called osteonecrosis of the jaw."

Ask your cancer team and your dentist how to plan dental work while you take one of these drugs.

NIAMS lists exercise, good nutrition and fall prevention as the non-drug parts of bone care. Fall prevention counts as much as bone density does. A bone only breaks if something breaks it.

Some people need different rules. That includes anyone with cancer in the bone, a healing fracture, or a spine bone that has already collapsed. The usual weight-bearing advice may not fit you. Ask for written activity limits from the team that has seen your scans. Ask a physical therapist to set the program.

A spine bone can collapse suddenly. MedlinePlus says this pain is "often sharp and 'knife-like'" and that it "can be disabling, and take weeks to months to go away." Height loss of up to 6 inches, or 15 centimeters, can build up over time.

Get urgent medical help if back pain comes with any of these signs.

• Numbness.
• Tingling.
• Weakness.
• Trouble walking.
• Loss of control of the bowel or bladder.

These can mean pressure on the spinal cord. MedlinePlus also says to contact your provider if your symptoms are getting worse. The same goes for problems controlling bladder and bowel function.

Report new or changing back pain to the cancer team. Do not treat it at home with a heat pack and a wait-and-see week.

Bone risk builds up over years. The record usually sits in several different systems. Keep your own copy of these items.

• The exact hormone drug, its start date, and its stop date.
• How long you took steroids, and at what dose.
• Which radiation fields included bone.
• Every DXA result: date, sites scanned, the score, and whether it was a T-score or a Z-score.
• Where each scan was done.
• Any fracture, and exactly how it happened.

That last point matters more than it sounds. A bone that breaks in a fall from standing height is a different signal than one broken in a car crash.

• Late Effects of Cancer Treatment — National Cancer Institute
• Hormone Therapy for Prostate Cancer — National Cancer Institute
• Hormone Therapy for Breast Cancer — National Cancer Institute
• Anastrozole — MedlinePlus Drug Information
• Hormone therapy for breast cancer — MedlinePlus Medical Encyclopedia
• Bone Density Scan — MedlinePlus Medical Test
• Bone mineral density test — MedlinePlus Medical Encyclopedia
• Bone Mineral Density Tests: What the Numbers Mean — NIAMS
• Osteoporosis — MedlinePlus Medical Encyclopedia
• Medicines for osteoporosis — MedlinePlus Medical Encyclopedia
• Compression fractures of the back — MedlinePlus Medical Encyclopedia
• Osteoporosis: Diagnosis, Treatment, and Steps to Take — NIAMS