Strontium ranelate (2 g/day) was studied in 5082 postmenopausal women. A reduction in incident vertebral fracture risk by 40% was shown after 3 years. This effect was independent of age, initial BMD, and prevalent vertebral fractures.
Introduction: Strontium ranelate is an orally active treatment able to decrease the risk of vertebral and hip fractures in osteoporotic postmenopausal women. The aim of this study was to assess the efficacy of strontium ranelate according to the main determinants of vertebral fracture risk: age, baseline BMD, prevalent fractures, family history of osteoporosis, baseline BMI, and addiction to smoking.
Materials and Methods: We pooled data of two large multinational randomized double-blind studies with a population of 5082 (2536 receiving strontium ranelate 2 g/day and 2546 receiving a placebo), 74 years of age on average, and a 3-year follow-up. An intention-to-treat principle was used, as well as a Cox model for comparison and relative risks.
Results: The treatment decreased the risk of both vertebral (relative risk [RR] = 0.60 [0.53–0.69] p < 0.001) and nonvertebral (RR = 0.85 [0.74–0.99] p = 0.03) fractures. The decrease in risk of vertebral fractures was 37% (p = 0.003) in women <70 years, 42% (p < 0.001) for those 70–80 years of age, and 32% (p = 0.013) for those ≥80 years. The RR of vertebral fracture was 0.28 (0.07–0.99) in osteopenic and 0.61 (0.53–0.70) in osteoporotic women, and baseline BMD was not a determinant of efficacy. The incidence of vertebral fractures in the placebo group increased with the number of prevalent vertebral fractures, but this was not a determinant of the effect of strontium ranelate. In 2605 patients, the risk of experiencing a first vertebral fracture was reduced by 48% (p < 0.001). The risk of experiencing a second vertebral fracture was reduced by 45% (p < 0.001; 1100 patients). Moreover, the risk of experiencing more than two vertebral fractures was reduced by 33% (p < 0.001; 1365 patients). Family history of osteoporosis, baseline BMI, and addiction to smoking were not determinants of efficacy.
Conclusions: This study shows that a 3-year treatment with strontium ranelate leads to antivertebral fracture efficacy in postmenopausal women independently of baseline osteoporotic risk factors.