Bone Health After Cancer
People who have received or are actively receiving certain cancer therapies are at an increased risk for developing osteoporosis. Osteoporosis and osteopenia (the precursor to osteoporosis) are medical terms for decreases in bone density, or a "thinning" of the bones, which increases the risk of fracture (breakage) of the affected bones. The disease most often affects the hips, spine and wrists, and is responsible for 2 million fractures a year in the U.S. Cancer survivors at risk for osteoporosis should take steps to prevent the disease and have appropriate screening.
Our bones provide support and structure for our body, as well as storage for essential nutrients. Your bones are continually being damaged and repaired by a complex system involving osteoclasts, which are cells that break down old bone, and osteoblasts, which are cells that form new bone. The body maintains a delicate balance between the breakdown of old or damaged bone and the formation of new bone, also known as bone remodeling, to maintain bone strength. Estrogen, parathyroid hormone and testosterone play critical roles in regulating bone remodeling. In osteoporosis, more bone is being destroyed than is being formed, leading to weakened bones.
Who is at risk?
- Women who have premature (early) menopause or decreased estrogen production due to cancer therapy (i.e. women taking hormonal therapy, such as aromatase inhibitors or leuprolide; or menopause induced by surgery, chemotherapy or radiation). Of note, tamoxifen increases the risk of osteoporosis in premenopausal women, but can actually increase bone density in menopausal women, thereby decreasing the chance of osteoporosis.
- Men who have decreased testosterone production. This is a factor for men treated with androgen deprivation therapy (ADT) such as leuprolide or orchiectomy (surgery to remove testicles).
- Treatment with ifosfamide, methotrexate, radiation to the brain or weight bearing bones (spine, hips, legs) or allogeneic stem cell or bone marrow transplant.
- Survivors of childhood cancers.
- Long-term use of corticosteroids (dexamethasone and prednisone, greater than 5mg per day for 2 months or more).
- Patients who have had their stomach surgically removed (gastrectomy).
There are additional risk factors that are not specific to having cancer, such as smoking, consuming excessive alcohol, leading an inactive lifestyle, being petite and thin, having a diet low in calcium and vitamin D, and missing menstrual periods. Osteoporosis is more common in women (80% women, 20% men), those with a family history, Caucasians and those of Asian or Latino descent, although all races have some risk. You can learn more about other risk factors by visiting the National Osteoporosis Foundation.
How is osteoporosis detected?
Screening for osteoporosis is done with a bone mineral density (BMD) test, of which a DEXA scan is the most commonly used. For the general public, screening is recommended to begin for women at age 65 (then every 2 years thereafter) and, for men, a baseline at age 70. Experts recommend screening for all female postmenopausal cancer survivors who have one or more risk factors (regardless of age), and to repeat the test every year. Men who are undergoing ADT or orchiectomy should have a baseline screening, with further testing depending on their results and risk factors. Cancer survivors should discuss their specific risk and need for screening with their healthcare team. Risk can be evaluated using the FRAX® tool, which was developed by the World Health Organization to evaluate the risk of fracture in people.
What can I do to protect my bone health?
While you may not be able to change your family and health history, there are some steps you can take to protect your bones.
- Do not smoke or drink excessive alcohol (no more than 2 drinks per day).
- Watch your caffeine intake- studies have shown large amounts of caffeine increase the risk of fractures (broken bones). Drink milk instead!
- Get your weight-bearing exercise or resistance training! This strengthens bones and muscles. Examples of weight-bearing exercise include aerobics, dancing, jogging and walking – anything that requires you to be upright and supporting your weight. Resistance training includes lifting weights, using exercise bands and Pilates.
- Have appropriate bone health screening.
- Get 1000mg of calcium (1200mg if >50 years old) and 400-800 international units (iu) of Vitamin D per day (800-1000iu if >50). This can be through supplements and/or in your diet, although most people have trouble meeting these requirements through diet alone.
Our bodies cannot produce calcium, so we must be sure to get enough in our diet to support healthy bones. On the nutritional label of a food that contains calcium, you will see "calcium" followed by a percentage, which is the percentage of the recommended daily amount (RDA) (1000 mg). A label reading 20% calcium means the product has 200mg of calcium per serving (multiply the percentage by 10 to get the mg of calcium per serving). For example, a typical 8 oz. glass of milk has 30% of the RDA, or 300mg. You should aim for the recommended 1000 – 1200 mg per day as noted above.
Dairy foods, such as milk, yogurt and cheese, are highest in calcium. Dark, green vegetables, such as broccoli, kale and collard greens, contain calcium as well. Some foods are fortified with calcium, but read the labels to get an idea just how much they contain. Calcium fortified orange juice is one good source. Spinach and rhubarb contain calcium, but also contains large amounts of oxalate and phytate, which prevent the body from absorbing their calcium. However, they do not interfere with the absorption of calcium from other foods. Other good sources of calcium include almonds, sunflower seeds, apricots and figs.
Calcium supplements are an easy way to get the recommended daily amount and come in 2 forms: calcium carbonate and calcium citrate. The body does have some trouble absorbing large amounts of calcium, so supplements should be split into 2 or more doses per day. Calcium carbonate requires stomach acid to be absorbed by the body, therefore people that take acid reducers (such as Zantac, Tagamet) and/or proton pump inhibitors (such as Prilosec, Prevacid, etc) should use calcium citrate. If you have trouble tolerating your calcium supplement, talk to your doctor or nurse; there may be another formulation you can tolerate more easily.
Vitamin D is often called the "sunshine vitamin" because our skin converts ultraviolet rays from the sun into vitamin D. In general, 10-15 minutes of sun exposure on the hands, arms and face creates the needed amount. However, it is difficult to measure how much vitamin D you are getting by this method and the amount can vary by season or location. Very few foods contain vitamin D naturally; these include certain fish (salmon, tuna) and fish liver oils, while egg yolks and beef liver contain small amounts. Many foods are fortified with vitamin D, once again, read the nutrition labels to know how much! You may notice that vitamin D is available in two forms, D2 and D3. Supplements typically contain D3. Research has found that both are beneficial for bone health. A cup of fortified milk contains about 100 international units (iu) of vitamin D. A multivitamin contains 400iu and some calcium supplements also include vitamin D. You should aim for 400-800iu per day (800-1000iu for women over 50). Talk to your doctor or nurse about whether or not you should have your Vitamin D blood levels checked.
If your healthcare team determines that you have osteoporosis or osteopenia, they may recommend medications to prevent it from getting worse. The main category of medication used to treat osteoporosis is called antiresorptive medications, which work by slowing the rate of bone breakdown. While breakdown is slowed, the formation of bone occurs at the same speed, which may allow bone density to improve. Antiresorptive medications include bisphosphonates (such as alendronate, zoledronic acid, etc.), raloxifene (a selective estrogen receptor modifier or SERM) and calcitonin. PTH (teriparatide) is a type of parathyroid hormone, which increases the rate of bone formation, allowing bones to strengthen, but is much less commonly used because of significant side effects. If you are taking a bisphosphonate, be sure to talk to your doctor or nurse if you have major dental work planned; you may need to temporarily hold this medication.
Each of the medications has some risk of side effects and may not be appropriate for every patient. Discuss your medical options for treating osteoporosis with your healthcare team.
WHO FRAX® tool (for estimating the risk of developing a bone fracture)