Your risk of osteoporosis (bone thinning) can be affected by breast cancer treatment and other treatments that lower your oestrogen levels.
Cancer treatment and osteoporosis risk
Osteoporosis is thinning of the bones so that they become more brittle. This increases the risk of breaking (fracture).
Our bones start to thin after the age of 35 or so, as part of the natural ageing process. But this is not usually noticeable.
Any cancer treatment in women that lowers oestrogen levels can increase the risk of osteoporosis. These treatments include:
- chemotherapy that caused an early menopause
- hormone therapy with a drug called an LHRH analogue (eg Zoladex)
- hormone therapy with a drug called an aromatase inhibitor (such as anastrozole, exemestane or letrozole)
- radiotherapy to your ovaries to stop them working
- surgery to remove your ovaries when you were premenopausal
Rates of bone loss
Tamoxifen for breast cancer usually only reduces bone density by a small amount. In postmenopausal women, aromatase inhibitors increase bone loss at an average rate of 1 to 3% per year. In young women who have had ovarian suppression followed by aromatase inhibitor therapy, bone density is lost at an average of 7 to 8% per year. Treatment with tamoxifen for 2 to 5 years before having aromatase inhibitors may slow down the rate of bone loss.
Women who have had an early menopause (before the age of 45) due to cancer treatment or who have ovarian suppression therapy and aromatase inhibitors are at higher risk of bone loss.
If you are having breast cancer treatment it makes sense to discuss your possible risk of weaker bones with your cancer specialist. There are steps you can take to help keep your bones healthy.
Who to talk to about your risk
Talk to your doctor or nurse specialist if you’re worried about bone thinning.
UK guidelines recommend that women taking hormone therapy for breast cancer who are at high risk of osteoporosis:
- should have their bone density measured before starting hormone therapy treatment
- should also have regular bone density checks during treatment
The test used is called a dual energy X-ray absorptiometry scan (DEXA scan) of bone mineral density (BMD).
Helping to prevent osteoporosis
There are several ways you can help to lower your osteoporosis risk.
- Make sure you get enough calcium in your diet.
- Cut down on caffeine and alcohol – they can interfere with your body’s calcium levels.
- Don’t smoke – it increases osteoporosis risk.
- Make sure you take enough exercise to build up your bones.
Getting enough calcium in your diet
An average adult should have about 700mg of calcium every day for good bone health.
There’s no evidence to suggest that women with breast cancer need any extra calcium. But if you already have osteoporosis, more calcium could help – between 1,000 and 1,200mg a day.
Our main dietary source of calcium is dairy products. You’re unlikely to be short of calcium if you eat a normal, balanced diet including dairy foods. But some women with breast cancer don’t like to eat dairy foods.
Main sources of calcium
You get the most calcium from milk, cheese and yoghurt. But if you don’t eat dairy foods, there is also calcium in:
- green vegetables, such as cabbage, broccoli and okra
- soya products, including tofu
- tinned fish where you eat the bones (sardines, salmon and pilchards)
- dried fruit
- fortified breakfast cereals
- bread and other foods made from flour (all UK white flour is enriched with calcium and wholemeal flour contains it naturally)
Other sources of calcium
There is calcium in tap water, but the amount varies depending on how hard the water is in your area. Some fruit juices and bottled waters have added calcium. Substitute milks, such as rice milk, oat milk and soya milk can also have added calcium. Check the label to find out how much they contain.
You could take supplements instead of calcium rich foods. Dieticians don’t recommend that you take more than the amount you should have in a normal diet. Too much calcium can be harmful.
The Food Standards Agency says that taking up to 1,500mg a day is unlikely to do any harm.
Getting enough vitamin D
For your body to use calcium, you also need vitamin D. Your body needs sun to make vitamin D. If you like being outside, then you probably get enough during the summer months to give you a vitamin D supply for a year. But if you are out in the sun, remember to protect against skin cancer with sunscreen. There is added vitamin D in margarine. It’s also found in oily fish and egg yolk.
You may want to ask your specialist or breast care nurse for a referral to a dietician at the hospital. A dietician can help you to work out whether you are getting enough calcium and vitamin D in your diet.
Exercise and bone health
Exercise is important for bone health. But it has to be weight bearing exercise. Swimming doesn’t help, because your bones aren't supporting your weight.
It’s great if you already take part in sport. But many of us don’t take enough regular exercise. The best way to start to tackle this is to try and bring exercise into your daily life.
- walking is good
- household activities can also help, such as cleaning, gardening, shopping or even going up and down stairs
- you could join an exercise group or class – it doesn’t have to be very energetic, gentle controlled exercise such as Tai Chi can be good
- although swimming doesn’t help, exercise classes that you take at the swimming pool (aqua aerobics) can, because of the resistance of the water.
The most important thing is that you get into the habit of exercise, however you choose to do it.
Bisphosphonate treatment for osteoporosis
Research trials have shown that drugs called bisphosphonates can prevent or slow bone loss in postmenopausal women taking aromatase inhibitor therapy.
Your doctor will take into account your own bone density levels and your risk of losing more bone density, when deciding whether you need to start bisphosphonate treatment.
Women who have had an early menopause and are taking aromatase inhibitor therapy are most likely to benefit from bisphosphonates.
Bisphosphonates can maintain bone strength and may help to prevent breast cancer from spreading to the bones. Studies are looking at whether taking bisphosphonates can help women with breast cancer to live longer.
Types of bisphosphonates
There are several different types of bisphosphonates, including:
- zoledronic acid (Zometa)
- ibandronic acid (Bondranat)
- disodium pamidronate (Aredia)
- sodium clodronate (Bonefos, Loron)
How you have bisphosphonates
You have clodronate and ibandronate either as a tablet or by drip into your vein (infusion). You have zoledronic acid and pamidronate as a drip.
You can also take a weekly bisphosphonate tablet for osteoporosis. This is called aledronate (Fosamax).
Bisphosphonates can cause side effects, such as an upset stomach and flu like symptoms. They can also affect the way your kidneys work.
You can find out more about these drugs and their side effects in our section on individual cancer drugs.
More information about osteoporosis
The National Osteoporosis Society has a lot of information on the causes, prevention and treatment of osteoporosis.
They also have guidelines for doctors treating women with hormone therapy for breast cancer.