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Stay Bone-Healthy

In addition to all the other rotten tricks advanced prostate cancer plays on a man, here’s a biggie:  It messes with your bones.  Moreover, androgen deprivation therapy (ADT) and androgen receptor-blocking drugs can also raise your risk of bone fracture.  But there’s good news: you can do a lot to protect your bones!

Being bone-savvy is the key to staying bone-healthy.

The first thing to know is that prostate cancer really likes bone.  In 90 percent of men who have metastatic prostate cancer, metastasis happens in the bone.  Prostate cancer causes changes in two different types of bone cell that, confusingly, sound a lot alike:  osteoblasts and osteoclasts.

Osteoblasts can make the bone thicker, denser, and hard, like concrete.  But this doesn’t mean the bone is stronger, says Harvard medical oncologist Matthew Smith, M.D., Ph.D., Director of the Genitourinary Oncology Program at Massachusetts General Hospital Cancer Center. “Even though it might seem dense on an X-ray, there are dents, also called sclerotic or osteoblastic bone lesions, and the bone is structurally weak.”  Osteoclasts also cause bone to become more brittle.

However: bone metastases can be treated.  There are several good bone-targeting drugs that zero right in on these lesions, including radium-223 (Xofigo), as well as supportive care treatments such as zoledronic acid (Zometa), and denosumab (Xgeva).  Bone metastases can also be treated with stereotactic body radiation therapy (SBRT), intense, highly precise doses of radiation.  Treating the cancer in the bones not only improves quality of life; it can improve survival, as well.

A second issue is that ADT raises your risk of osteoporosis.  If you are on ADT, whether or not you have metastasis in the bone, “you are separately at risk for accelerated bone loss and greater risk for osteoporotic fractures from a fall or minor trauma,” says Smith.  So, to sum up: “Men who are on systemic treatment for prostate cancer are at risk for osteoporotic fractures, and patients with bone metastases, additionally, are at risk for skeletal complications.”

By “systemic treatment,” Smith doesn’t just mean ADT, but androgen directed therapies such as enzalutamide, apalutamide, or abiraterone, which add their own wrinkle: “They increase the risk of falls, likely due to their effect on the central nervous system.  It’s kind of a bad setup:  if you’re on long-term ADT, you can lose bone mass and have a greater risk for fracture.  Add a second drug – and these are meaningful and important drugs – and the unintended consequence is a greater risk for falls in men who are already vulnerable.”

Oh, no!  So, what’s the plan?  Should every man who starts ADT immediately start taking a bone-protective agent (such as zoledronic acid or denosumab) to prevent osteoporosis?  No, says Smith.  “If we did that, we would be overtreating, with a drug that many men don’t need.”  And why is this?  Because “osteoporosis and fractures are not an inevitable consequence of ADT.  Not every man is going to develop osteoporosis and fractures.”  To repeat:  Osteoporosis is not a done deal!  “Osteoporosis drugs have their own side effects; we don’t want to do more harm than good.”

Thus, Smith says, what makes the most sense for men on ADT is to evaluate everyone, and intervene only in patients at risk, “for whom osteoporosis treatments would do more good than harm.  In my opinion, the best method of doing that is using the very thoughtful guidelines developed by the National Osteoporosis Foundation for fracture prevention in men.  We don’t have to reinvent the wheel.  There are abundant evidence-based recommendations; we just need to apply those principles.”

Are you at higher risk?  A good place to begin is an assessment tool called FRAX. Smith notes that “it just takes a couple minutes to put in the information and get results, and then you’ll have a good idea of your risk based on clinical features: your age, height, and weight, and your bone mineral density measurement, if you know it.”  Smith recommends that men get a baseline bone density scan at the time they start ADT.  “Some patients should have prompt intervention to reduce their risk of fractures.  Others would do better just to be followed.   I typically repeat the bone density scan after a patient has been on ADT for a couple of years.”  Note:  “If you are only undergoing a short course of ADT, your risk is basically the same as that of the general population,” says Smith.  “The risks of short-term ADT are very different from those of lifelong ADT.”

What else can you do?  Should you be taking a horse-pill-sized dose of calcium?  Smith says no; it’s better to help your bones through a good diet.  “Diet, not supplements, and vegetables rather than lots of dairy.”  Dark and leafy greens, such as kale, collard greens, and bok choy, have calcium.  They also have bone-strengthening vitamin K.  Sweet potatoes have magnesium and potassium, which your bones need.  Fatty fish, like salmon, has vitamin D, which helps your bones absorb calcium, and the omega-3 fatty acids are also good for bones.   Conversely:  Drinking alcohol and smoking cigarettes both increase your risk of falling.  (For more on the benefits of brightly-colored vegetables, download PCF’s guide, The Science of Living Well, Beyond Cancer.)

“Another issue with ADT is that men tend to gain weight and lose muscle,” says Smith.  But you can fight what ADT does to your metabolism with regular physical activity, “30 minutes a day, five days a week at least.”  Don’t be alarmed:  you don’t have to start training for a triathlon!  Just walking or riding an exercise bike can help a lot!  “Some weight-bearing exercise will have a beneficial effect on your bone mass, but more importantly, it will reduce your risk for a fall.”  The key here, he adds, is “use it or lose it.  If you spend most of your time being sedentary, when you do walk, you are at a greater risk of having a fall.”

Take vitamin D.  Vitamin D helps your body absorb calcium.  Smith says this is the one dietary supplement that he does recommend:  2000 IU a day.

And, take heart:  “Osteoporosis and fractures are not inevitable, and for patients at greater risk, they are preventable.  If necessary, we can intervene with medicine to reduce the risk for fractures.”  Lifestyle changes – eating bone-strengthening foods and exercising, cutting out smoking and alcohol – can make a big difference, too.  “It is not at all the case that there’s nothing you can do.  You can do a lot!”

Janet Worthington
Janet Farrar Worthington is an award-winning science writer and has written and edited numerous health publications and contributed to several other medical books. In addition to writing on medicine, Janet also writes about her family, her former life on a farm in Virginia, her desire to own more chickens, and whichever dog is eyeing the dinner dish.