A roundup of medical and other interventions that make a difference (or don’t, in some cases)
IN THIS ARTICLE
The past year has seen continuing variety in pharmaceutical and nonpharmaceutical approaches to osteoporosis, which remains—and will remain—a significant source of morbidity and mortality as the Baby Boom generation ages. As more people who are less healthy live longer, the sequelae of fragility fractures, mainly of the hip and spine, will increase as well, unless we continue to make strides in the identification of risk and in the prevention, detection, and treatment of osteoporosis.
In this article, I highlight:
- two trials of the newly FDA-approved denosumab (Prolia) that demonstrate its benefits and risks
- a recent report on osteonecrosis of the jaw in bisphosphonate users, including low-risk women taking an oral formulation
- guidance from Canada on how to derive maximum benefit from vitamin D
- disappointing findings on the benefits of resistance training for women
- two studies detailing the benefits of another SERM, lasofoxifene.
Denosumab outperforms alendronate as well as placebo
Cummings SR, San Martin J, McClung MR, et al; for FREEDOM Trial. Denosumab for prevention of fractures in postmenopausal women with osteoporosis. N Engl J Med. 2009;361(8):756–765.
Brown JP, Prince RL, Deal C, et al. Comparison of the effect of denosumab and alendronate on bone mineral density and biochemical markers of bone turnover in postmenopausal women with low bone mass: a randomized, blinded, phase 3 trial [published online ahead of print December 14, 2009]. J Bone Miner Res. doi:10.1359/jbmr.080910.
In their report from the FREEDOM trial (Fracture Reduction Evaluation of Denosumab in Osteoporosis Every 6 Months), Cummings and colleagues describe this prospective, placebo-controlled study of 7,868 postmenopausal women, all with a T-score worse than –2.5. Participants were randomized to 60 mg of subcutaneous denosumab or placebo every 6 months for 3 years. Those taking denosumab experienced a 68% reduction in the rate of new vertebral fracture (P < .001), a 20% reduction in nonvertebral fracture (P =.02), and a 40% reduction in hip fracture (P =.04), compared with placebo.
Denosumab is a fully human monoclonal antibody against the receptor activator of RANKL, which is a cytokine essential for the formation, function, and survival of osteoclasts. By binding to RANKL, denosumab prevents the usual interaction between RANKL and its receptor on osteoclast precursors and osteoclasts. And by preventing this interaction, denosumab reversibly inhibits osteoclast-mediated bone resorption, thereby reducing bone turnover and increasing bone mineral density (BMD).
Denosumab received FDA approval in June 2010 for the treatment of osteoporosis in postmenopausal women who have a high risk of fracture (defined as a history of osteoporotic fracture, the presence of multiple risk factors for fracture, or the failure of or intolerance to another form of osteoporosis therapy).
Details of the FREEDOM trial
The average age of women in the trial was 72.3 years (range, 60 to 90 years). At baseline, 23% of participants had a preexisting vertebral fracture. The primary endpoint was new vertebral fracture, with nonvertebral fracture and hip fracture as secondary endpoints.
No significant differences were found between denosumab and placebo in:
- total incidence of adverse events
- serious adverse events
- discontinuation of treatment because of adverse events
- overall incidence of cancer
- overall incidence of cardiovascular events
- adverse or serious adverse events of infection
- local reactions at the site of injection.
No neutralizing antibodies developed in either group.
Four cases of opportunistic infection were reported in the denosumab group, and three were reported in the placebo group. Eczema was reported by 3% of women in the denosumab group, versus 1.7% in the placebo group (P < .001). Falls that were not associated with a fracture were reported by 4.5% of subjects taking denosumab, versus 5.7% of those taking placebo (P =.02). Flatulence was more common among women taking denosumab (2.2%) than among those taking placebo (1.4%) (P =.008). Twelve women (0.3%) in the denosumab group reported serious adverse events of cellulitis, compared with one woman taking placebo (<0.1%) (P =.002).
Seventy women (1.8%) died in the denosumab group, compared with 90 (2.3%) in the placebo group (P =.08).
Denosumab versus alendronate
Brown and associates compared denosumab and alendronate in a randomized, blinded trial of 1,189 postmenopausal women who had a T-score worse than –2.0 at the lumbar spine or total hip. At month 12, denosumab significantly increased BMD at the total hip, compared with alendronate (3.5% versus 2.6%) (P < .0001). Compared with alendronate, denosumab also increased BMD in the:
- femoral neck (0.6%)
- trochanter (1.0%)
- lumbar spine (1.1%)
- 1/3 radius (0.6%) (P ≤ .0002 for all sites).
Denosumab led to significantly greater reduction of bone turnover markers than did alendronate therapy. Unlike bisphosphonates, denosumab is not retained in bone.
Participants were randomized 1:1 to:
- 60 mg subcutaneous denosumab injection every 6 months plus oral placebo weekly (n=594)
- 70 mg of oral alendronate weekly plus subcutaneous placebo injections every 6 months (n=595).
BMD was assessed at 6 and 12 months, and bone turnover markers were assessed at 1, 3, 6, 9, and 12 months. Safety was evaluated by monitoring adverse events and laboratory values.
No significant difference between denosumab and alendronate was observed in the overall incidence of adverse events (80.9% versus 82.3%, respectively) (P =.60), including gastrointestinal disorders, infections, and neoplasms. Most adverse events were mild or moderate in severity. Treatment-related adverse events were similar between groups (17% and 18.3% for denosumab and alendronate, respectively). Similar numbers of women experienced serious adverse events (34 women [5.7%] taking denosumab versus 37 [6.3%] taking alendronate). The overall safety profile was similar for both drugs.
Is osteonecrosis of the jaw a concern with denosumab?
The package insert for Prolia mentions that osteonecrosis of the jaw (ONJ) can “occur spontaneously, is generally associated with tooth extraction and/or local infection with delayed healing and has been reported in patients receiving Prolia.”
Although no cases of ONJ were reported in the FREEDOM trial, a letter by Kyrgidis and Toolis to Osteoporosis International makes the point that ONJ may not be related solely to bisphosphonate use.1 Taylor and colleagues described a case of a cancer patient who had never taken a bisphosphonate but who was treated with denosumab and later developed ONJ.2 Kyrgidis and Toolis refer to presentations in the European Journal of Cancer Supplements that reported on head-to-head trials of denosumab and intravenous zoledronic acid in the treatment of bone metastases in cancer patients.1 In one trial, the incidence of ONJ with denosumab was 2.0%, compared with 1.4% for zoledronic acid (P =.31). In another trial, the incidence of ONJ was 1.1% for denosumab and 1.3% for zoledronic acid (P =1.0). Kyrgidis and Toolis concluded that the association between ONJ and denosumab appears to be somewhat dose-related, as it is with bisphosphonate-related ONJ.
Plausible mechanisms for denosumab-related and bisphosphonate-related ONJ include defective osteoclast differentiation, function, survival, and “fatigue.”
Because denosumab has a shorter clearance time than bisphosphonates do, it seems feasible that treatment of denosumab-related ONJ will be easier and healing earlier than with bisphosphonate-related ONJ.
WHAT THIS EVIDENCE MEANS FOR PRACTICE
Denosumab is a highly effective, safe treatment for patients who have osteoporosis and who are at high risk for fracture. Its twice-yearly administration can significantly enhance compliance, compared with drugs that are taken orally either weekly or monthly. While the drug may appear to be expensive, its cost should be “amortized” over 6 months, rendering its expense roughly equivalent to that of daily, weekly, or monthly products.
Although denosumab is injectable, it is an effective first-line drug for patients who have a high risk of fracture.
Otto S, Abu-Id MH, Fedele S, et al. Osteoporosis and bisphosphonates-related osteonecrosis of the jaw: Not just a sporadic coincidence—a multi-centre study [published online ahead of print June 25, 2010]. J Craniomaxillofac Surg. doi:10.1016/j.jcms.2010.05.009.
ONJ is a serious side effect well known to practitioners of maxillofacial surgery.3 Most research into the condition has focused on patients who have bone metastasis who have received intravenous bisphosphonates. In this report, Otto and colleagues describe a large multicenter trial at 11 European centers from 2004 through 2008. ONJ occurred in 470 patients taking a bisphosphonate. Each case was clinically examined, and a detailed history was supplied.
Although more than 90% of these cases were associated with intravenous bisphosphonate use, mainly in cancer patients who had bony metastasis, 37 cases (7.8%) occurred in women taking an oral bisphosphonate for osteoporosis. Of these, only 43% had any of the risk factors defined by the American Association of Oral and Maxillofacial Surgery (such as duration of bisphosphonate use and previous dental procedures). That means that 57% of these cases would be considered low-risk.
In this group of oral bisphosphonate users, patients tended to be older and had been on bisphosphonate therapy longer than patients in the high-risk group. Overall, 78% of the oral users who developed ONJ had been taking a bisphosphonate longer than 3 years.
WHAT THIS EVIDENCE MEANS FOR PRACTICE
ONJ is most common in older patients who have been taking an oral bisphosphonate for a long time. Even so, the incidence of ONJ remains quite low, and the potential morbidity pales in comparison with the benefit of fracture reduction in appropriately selected patients.
These reports should not deter clinicians and patients from using effective treatments to prevent fracture in osteoporotic patients.
Hanley DA, Cranney A, Jones G, et al; for the Guidelines Committee of the Scientific Advisory Council of Osteoporosis Canada. Vitamin D in adult health and disease: a review and guideline statement from Osteoporosis Canada. CMAJ. 2010;182(12):E610-E618.
The Institute of Medicine is expected to release a comprehensive report on Vitamin D late this fall. In the meantime, the Guidelines Committee of the Scientific Advisory Council of Osteoporosis Canada has published its own set of guidelines that underscores the importance of adequate vitamin D intake to ensure bone health and help prevent osteoporosis.
Here are a few points taken from these guidelines:
• Vitamin D is an essential nutrient in the prevention of osteoporosis. It may reduce the risk of other medical disorders unrelated to bone and mineral metabolism.
• Vitamin D3 may be better utilized in the body. After synthesis in the skin or dietary ingestion, vitamin D is removed from the bloodstream into various tissues, including the liver, adipose tissue, and muscle. Its biologic half-life is about 60 days, and it is eventually converted to 25-hydroxyvitamin D in the hepatocytes. Vitamin D3 (cholecalciferol) is the molecule synthesized in the skin in response to ultraviolet B radiation, whereas vitamin D2 (ergocalciferol) is derived from irradiation of certain fungi. Both vitamin D2 and vitamin D3 create 1,25-dihydroxyvitamin D, the active form, although there is some evidence that vitamin D2 may not be used in the body as efficiently as vitamin D3. Most vitamin D supplements consist of vitamin D3, but high-dose preparations, available by prescription, are vitamin D2.
• Vitamin D deficiency is a continuum. The term “deficiency” was previously used to describe the advanced clinical effects of chronically low vitamin D. “Insufficiency” described a milder form of deficiency in which reduced absorption of calcium and the resultant mild secondary hyperparathyroidism might increase bone loss.
• Don’t rely on sunlight. Ultraviolet B radiation (wavelength 290–315 nm) promotes synthesis of vitamin D. The amount of exposure needed to achieve adequate vitamin D status depends on latitude, altitude, time of year and day, weather, other environmental characteristics, age, skin pigmentation, clothing, activity, and the amount of skin irradiated. The influence of diet on vitamin D status is minimal, and most circulating vitamin D is derived from exposure to sunlight. Dermatologists recommend that the safest course is to avoid exposure to the sun and to take vitamin D supplements.