Bone Basics

John Nidecker is a devoted cyclist, logging up to 100 miles a week near his home in Santa Rosa, Calif. He’s also a careful rider, knowing that accelerated bone loss is a side effect of intermittent hormone therapy for prostate cancer, a part of his life for the past 14 years.

“I’m conscious of the risk of falling, but it doesn’t hold me back too much,” says Nidecker, whose bone density scans consistently show low bone mass but above the osteoporosis range.

Osteoporosis, or thinning bones, is worrisome for people with cancer because it doesn’t necessarily take a fall off a bike to fracture a bone. Something as simple as a sneeze or a coughing fit can break a weakened rib. Vertebrae can break for no reason, causing a curved spine or, more ominously, a hip could get broken, leaving a patient bedridden for a time.

“The consequences of osteoporotic fracture can lead to death,” says Catherine Hall Van Poznak, an associate professor of medical oncology who studies osteoporosis and breast cancer at the University of Michigan in Ann Arbor. Nothing good comes from a bent skeletal frame that prevents organs from “maximizing their abilities,” she says. For example, when lungs aren’t expanding fully, they are more vulnerable to pneumonia. “The frailty that follows fractures increases an individual’s risk for additional illnesses.”

Many therapies used to treat breast and prostate cancers work by suppressing hormones that can fuel cancer, such as testosterone and estrogen. There’s a trade-off, though, because bodies need these hormones to keep bones strong.

Bones are living tissue in a constant cycle of renewal. In healthy bones, one category of cells (osteoclasts) dissolves bone tissue, while other cells (osteoblasts) rebuild, replacing the removed bone with new bone. The body needs calcium and vitamin D for the rebuilding process. As the body ages, osteoblasts fall behind, and ultimately there is a net loss of bone, increasing the risk for osteoporosis.

The consequences of osteoporotic fracture can lead to death. The frailty that follows fractures increases an individual’s risk for additional illnesses.”

One of estrogen’s important jobs is to maintain proper balance between bone buildup and breakdown, according to the National Cancer Institute. Yet, medicines used to treat hormone receptorpositive breast cancers affect bone density in different ways. Aromatase inhibitors (AIs) block the production of estrogen and are associated with an increased risk of osteoporosis and fracture. Selective estrogen receptor modulators (SERM), such as tamoxifen, work by blocking the effects of estrogen on cancer cells and some other tissues, but have the balancing effect of estrogen on bones.

“When discussing toxicity of aromatase inhibitors with postmenopausal women, we counsel them on the importance of calcium and vitamin D daily intake and doing weight-bearing exercise to mitigate the risk of bone loss,” Van Poznak says. “Diet and exercise are the foundation. Intervention with a prescription medication is only for those at greatest risk of osteoporotic fracture.”

A recent study concluded that all patients starting AIs “need advice regarding exercise and calcium/ vitamin D supplements.” In addition, they need bone mineral density monitoring and bone-building medication if bone mass numbers are below a certain threshold or they have at least two other fracture risk factors, such as a smoking history or family history of fractures.

[Read "Assessing the Risk"]

Osteoporosis medications that slow bone loss include bisphosphonates, such as risedronate, ibandronate, Fosamax (alendronate) and Zometa (zoledronic acid), as well as the biologic drug Prolia (denosumab), also known as Xgeva.

However, the Food and Drug Administration (FDA) issued a consumer update in 2012 suggesting that “some patients may be able to stop using bisphosphonates after three to five years and still continue to benefit from their use.” It also mentions that bisphosphonate labels have carried safety warnings about the rare side effect of severe jawbone decay (osteonecrosis of the jaw) since the early 2000s, and increased risk of unusual thigh bone fractures since 2010. The update cautions that the “FDA continues to evaluate a possible association of bisphosphonates with esophageal cancer.”

Though different types of cancer treatments create different levels of risk for bone loss, the National Comprehensive Cancer Network’s (NCCN) Task Force on Bone Health in Cancer Care recommends that cancer patients have bone density screening, regardless of age or gender, because patients “typically have several additional osteoporosis risk factors.”

The NCCN recommendation is welcome news to Nidecker, who requested a bone density baseline scan when he started receiving hormone deprivation treatments 14 years ago, after learning about it online. “Very little was explained to me,” he says. “I am kind of disappointed that none of the dozen doctors I talked to, with one exception, suggested a scan.”

Little has changed since then, if the men in his prostate cancer support groups are typical. Most are unaware of the side effects of hormone therapy. “Bone density in particular is not on anyone’s radar screen,” says Nidecker, who leads support groups at the University of California, San Francisco Medical Center at Mount Zion and at Sutter Health. His advice for anyone joining a group is to get a baseline test, especially those who are starting hormone therapy.

When Nidecker learned his Internet and discovered that one remedy is to increase calcium, vitamin D and a few other minerals through diet and supplements. “I also shifted to a more plantbased diet and put more emphasis on fitness.” He took Fosamax to counter bone loss for about five years, but stopped upon learning the potential longterm side effects of bisphosphonates.

Bone density in particular is not on anyone’s radar screen. We suggest they talk to their doctor about getting a baseline test, especially those who are starting hormone therapy.”

fear is staying alive and second is sexual function,” says Barbara Zoltick, an oncology nurse practitioner at the Abramson Cancer Center in Philadelphia. “My feeling is now that men are living longer with prostate cancer, they want to live better.”

Historically, there hasn’t been an emphasis on bone density testing for men, she says, but she sees that changing. In addition to receiving a DEXA (dual energy Xray absorptiometry) scan both before starting hormone deprivation therapy and again a year later, men are encouraged to pay attention to bone health, she says.

They should continue physical activity or take up weight-bearing activity, such as dancing or jogging, under guidance from a primary care doctor or a physical therapist, Zoltick adds. They also should follow current National Osteoporosis Foundation guidelines regarding calcium and vitamin D intake, either through food or over-the-counter supplements, and avoid excessive caffeine, smoking and alcohol consumption. Chronic steroid use can also contribute to thinning bones.

Few clinical studies of men receiving hormone therapy have been run to evaluate the effectiveness of calcium and vitamin D on bones, but their usefulness is “inferred from other studies,” Zoltick says. “Anecdotally, it’s hard to tell whether these lifestyle changes make a definitive change on bone because of so many variables,” which is why more clinical trials are needed, she says.

To stress the importance of shoring up bone health for men in treatment, she has teamed up with other nurse practitioners and a dietitian at the University of Pennsylvania to create clear instructions that are evidencebased and in accord with current guidelines. They want to ensure that patients are receiving consistent instructions from their medical team.

“Sometimes, giving patients too much paper to read is overwhelming,” Zoltick says. “We are trying to send them home with something very basic.”