Prostate Cancer and Bone Health

Why? Prostate cancer and its treatment can affect bone health.

Cancer Treatment-Induced Bone Loss (CTIBL)
Some prostate cancer treatments tend to decrease bone mineral density, thereby increasing the risk of fracture. Androgen deprivation therapy (also known as hormone therapy) can increase bone loss risk by decreasing a man’s testosterone levels. One study estimated that, among patients receiving androgen deprivation therapy, bone density decreased between 1.4% and 2.6% during years three to eight. Radiation therapy to the bone and some kinds of chemotherapy may also decrease bone density.

But bone loss can be prevented or treated. So ask your medical team some questions:
•    How might my prostate cancer diagnosis and my past and current treatments affect my bones?
•    Am I at an increased risk for bone loss?
•    What can I do to slow bone loss or increase my bone density?

Bone Metastases
In many, many men, prostate cancer never spreads beyond the prostate gland. However, when prostate cancer does metastasize, it tends to spread to the skeleton. From 65 to 75 percent of all patients with advanced (or metastatic) prostate cancer eventually develop bone metastases. Why? Well bone is constantly changing, renewing itself through the breakdown of old bone and the creation of new bone. What this means is that bone is rich in growth factors and provides a fertile environment for tumour cells. Cancer cells can weaken and destroy the bone around tumours, which can result in some serious complications, called skeletal-related events (SREs).

It is very important, consequently, to improve the bone health in men fighting advanced prostate cancer, and there is a growing body of research regarding how to do this. Here are some highlights:
•    Bisphosphonates, drugs that inhibit bone resorption (the process of breaking down and then building up bone), have been shown to reduce cancer-related bone complications and to delay the onset of SREs. Examples of bisphosphonates that have been used to prevent bone loss in men with advanced prostate cancer include pamidronate (Aredia®), alendronate (Fosamax®), ibandronate (Boniva®), and zoledronate (Zometa®). For more information, see the article “Them Bones: Osteoporosis and prostate cancer” in the January 2009 issue of Network News. 
•    A new drug, a monoclonal antibody called denosumab (Xgeva), was recently reported as being better than zolendronic acid for the prevention of skeletal-related events in men with advanced castration-resistant prostate cancer. (See the abstract of this study, which will be printed in the March 2011 issue of The Lancet.)
•    The injection of a special kind of cement into the bone of the vertebrae, a technique called vertebroplasty, has been used to treat bone metastases in the spine. Kyphoplasty, which uses a balloon to repair fractures and restore the vertebrae to the correct position, can be used in conjunction with vertebroplasty because it creates a mould for the cement.
•    Surgery can be used to reinforce bones that are at risk of breaking or to repair those that have already been broken.

So what can you, the prostate cancer survivor do to keep “them bones” as healthy as possible?

What Should I Do?

Report bone pain to your medical team.
Experiencing bone pain can be unsettling for prostate cancer survivors. But a number of conditions, including arthritis, injury, or osteoporosis, cause bone pain. It may not be cancer. And even if it is, you should find this out as quickly as possible. If pain persists for more than 7 to 10 days, make an appointment. Here are some other factors you might want to consider.

•    The pain caused by metastases usually does not occur in the joints.
•    Bone metastases cause pain that lingers; it does not just go away.
•    Other health issues can alert you to problematic bone health, e.g., loss of height, a fracture, or rising PSA.

Take steps to maintain healthy bones.
Although osteoporosis is sometimes considered an “older woman’s condition” (sound familiar?), men experience bone loss as they age too. Peak bone mass is achieved by both men and women in their 20s and 30s. After that age, we begin to lose bone density. Known risk factors include being thin, having a diet low in calcium, lack of exercise, smoking cigarettes, and consuming caffeine or alcohol excessively. So guess what it takes to maintain healthy bones?

•    Get enough calcium in your diet. The recommended amount for men over 50 is 1,200 mg each day. Soy and dairy products as well as green vegetables (e.g., broccoli and spinach) are good sources. (Note that eating a diet that is very high in calcium is being studied as a possible prostate cancer risk factor as well.)
•    Ask about taking a calcium supplement if you can’t meet the dietary recommendations. Your doctor may want to check your urine-calcium output to determine whether this step is optimal.
•    Get enough vitamin D. This vitamin helps us process calcium, and, in Canada, where the sun is not very strong for half the year, it is sometimes difficult to get enough of it. (Our bodies produce this vitamin when they are exposed to the sun’s ultraviolet rays.) Currently, the Canadian Cancer Society recommends 1,000 IU (or 25 micrograms) each day.  Research on vitamin D and prostate cancer is ongoing (see below).
•    Don’t smoke or quit if you do. 
•    Limit salt, protein, alcohol, and caffeine consumption. Salt reduces the body’s ability to use calcium, and too much protein prevents the body from retaining calcium. (Estimates are that men should have about 56 grams of protein every day, but most have double that amount.) Excessive drinking (consistently more than 2 or 3 drinks a day) and excessive caffeine consumption (consistently more than 4 cups a day of coffee or cola) increase the risk of osteoporosis.
•    Exercise. Try to engage regularly in weight-bearing exercise, such as walking, skating, or hiking, and some weight-resistance exercises. Recommendations are that you try to exercise each day for between 30 and 60 minutes. (You can break weight-bearing exercise into 5 to 10 minute segments and intersperse these with weight-resistance exercises, such as weight training.)

Ask your medical team about monitoring for bone loss.
Many things can affect whether you are at an increased risk of bone loss because of your prostate cancer diagnosis or treatment. For some men, bone loss is just not a concern. And often, by rights, issues such as bone loss take a back seat to more life-threatening ones, the cancer itself! What do these facts add up to? Sometimes bone health is overlooked. Consider the following:

•    Getting a bone density test prior to hormone therapy to establish a baseline value, and having your bone density evaluated annually if you continue to receive this therapy
•    Asking your doctor about testing your urinary output of calcium and your vitamin D levels
•    Alerting your dentist that you are being or have been treated for prostate cancer, and discussing dental procedures such as implants or the pulling of teeth with your oncologist or medical team
•    Keeping copies of bone scans and bone density tests in your files

References:

Boning up on the sunshine vitamin, CBC News, November 30, 2010

Dietary Reference Intakes, Health Canada

Fizazi, K., Carducci, M, & Smith, M., et al. (2011). Denosumab versus zoledronic acid for treatment of bone metastases in men with castration-resistant prostate cancer: a randomised, double-blind study. The Lancet, 377(9768), 813–822.

Guise T. A., & Eastham J. (2004). Cancer treatment induced bone loss in prostate cancer: Pathophysiology, preclinical findings, and treatment with zoledronic acid.
European Urology, 3(5), 46–54.

Osteoporosis Canada