Maintenance of antifracture efficacy over 10 years with strontium ranelate in postmenopausal osteoporosis

Abstract

In an open-label extension study, BMD increased continuously with strontium ranelate over 10 years in osteoporotic women (P < 0.01). Vertebral and nonvertebral fracture incidence was lower between 5 and 10 years than in a matched placebo group over 5 years (P < 0.05). Strontium ranelate's antifracture efficacy appears to be maintained long term.

Introduction: Strontium ranelate has proven efficacy against vertebral and nonvertebral fractures, including hip, over 5 years in postmenopausal osteoporosis. We explored long-term efficacy and safety of strontium ranelate over 10 years.

Methods: Postmenopausal osteoporotic women participating in the double-blind, placebo-controlled phase 3 studies SOTI and TROPOS to 5 years were invited to enter a 5-year open-label extension, during which they received strontium ranelate 2 g/day (n = 237, 10-year population). Bone mineral density (BMD) and fracture incidence were recorded, and FRAX® scores were calculated. The effect of strontium ranelate on fracture incidence was evaluated by comparison with a FRAX®-matched placebo group identified in the TROPOS placebo arm.

Results: The patients in the 10-year population had baseline characteristics comparable to those of the total SOTI/TROPOS population. Over 10 years, lumbar BMD increased continuously and significantly (P < 0.01 versus previous year) with 34.5 ± 20.2% relative change from baseline to 10 years. The incidence of vertebral and nonvertebral fracture with strontium ranelate in the 10-year population in years 6 to 10 was comparable to the incidence between years 0 and 5, but was significantly lower than the incidence observed in the FRAX®-matched placebo group over 5 years (P < 0.05); relative risk reductions for vertebral and nonvertebral fractures were 35% and 38%, respectively. Strontium ranelate was safe and well tolerated over 10 years.

Conclusions: Long-term treatment with strontium ranelate is associated with sustained increases in BMD over 10 years, with a good safety profile. Our results also support the maintenance of antifracture efficacy over 10 years with strontium ranelate.

Fig. 1

Flow of patients

Fig. 2

Cumulative incidence of new vertebral fracture (A), new nonvertebral fracture (B), and new osteoporotic fracture (C) in the 10-year population between 0 and 5 years’ treatment with strontium ranelate and between 6 and 10 years’ treatment with strontium ranelate (gray bars) and in the FRAX®-matched placebo group of TROPOS between 0 and 5 years (white bars)