OsteoEd

How effective is raloxifene in reducing the risk of fractures in postmenopausal women with osteoporosis?

Raloxifene resulted in a 30-50% decrease in the incidence of new vertebral fractures over a 3 year period in the Multiple Outcomes of Raloxifene Evaluation (MORE) study. This was a randomized, blinded, placebo-controlled trial of over 6,000 postmenopausal women with osteoporosis (1) (see Figure 1). A recent meta-analysis of seven clinical trials evaluating the anti-vertebral fracture efficacy of raloxifene found that the risk of fractures was reduced by 40%-49%(2).

The main points of the MORE study are:

• Study subjects were postmenopausal women with T-score below -2.5 (spine or hip) without previous fracture or T-score < -1.0 and prior vertebral fracture history.
• Results showed spine fracture reduction of 30 percent to 50 percent and no reduction in non-spine fractures (e.g., hip).
• The number needed to treat (NNT) for 3 years to prevent one spinal fracture is 42 with fracture history and 113 without fracture history (3).

Readers should be cautious about generalizing the results of this trial to postmenopausal women with osteopenia and no personal history of fractures, even if they have additional risk factors for osteoporosis. Both the control and treatment groups in this study received calcium (500 mg/d) and vitamin D (400-600 IU/d), so the effects of raloxifene therapy are in addition to those interventions (1).

Currently, there is no evidence that suggests that raloxifene decreases non-vertebral fractures. However, studies have demonstrated that raloxifene consistently improves bone mineral density at the lumbar spine and hip (4). The magnitude of this effect averages between 2 and 3% over a two to three year period. To the extent that bone mineral density is an important determinant of fracture risk, raloxifene may eventually prove effective in reducing non-vertebral fractures in a study with sufficient power to detect such an effect. Notably, the absolute levels of gain in bone mineral density with raloxifene seem to be lower than those seen with estrogen or alendronate.

Figure 1. Reduction in New Vertebral Fractures Among 6,828 Women Who Completed the MORE Study. Women did or did not have vertebral fracture at the beginning of study. RR indicates relative risk; CI, confidence interval (1). Copyright 1999, American Medical Association.

1. Ettinger B, Black DM, Mitlak BH, Knickerbocker RK, Nickelsen T, Genant HK, et al. Reduction of vertebral fracture risk in postmenopausal women with osteoporosis treated with raloxifene. JAMA 1999; 282: 637-45.
2. Seeman E, Crans GG, Diez-Perez A, Pinette KV, Delmas PD. Anti-vertebral fracture efficacy of raloxifene: a meta-analysis. Osteoporosis Int 2006; 17: 313-316.
3. McClung MR. Therapy for fracture prevention. JAMA 1999; 282: 687-689.
4. Cranney A, Adachi JD. Benefit-Risk assessment of raloxifene in postmenopausal osteoporosis. Drug Safety 2005; 25(8): 721-730.

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