Background/Purpose: Strontium ranelate has proven efficacy against vertebral and nonvertebral fractures in postmenopausal osteoporosis. We explored whether the effect of strontium ranelate on bone turnover markers is influenced by the presence of well-established risk factors for fracture (i.e. age, prevalent fractures, parental history of osteoporosis, low body mass index, and addiction to smoking).

Methods: Analysis of pooled data from two three-year randomized controlled trials (i.e. the Spinal Osteoporosis Therapeutic Intervention (SOTI) and Treatment Of Peripheral Osteoporosis (TROPOS) studies). Bone-specific alkaline phosphatase (BALP, immunoradiometric assay Tandem®-R Ostase® kit, Beckman Coulter, USA), C-terminal propeptide of type I procollagen (PICP, RIA, Orion Diagnostic) and serum C-terminal telopeptides (S-CTX, ELISA using the Serum CrossLaps® ELISA kit, Nordic Bioscience Diagnostics, Denmark) were assessed at baseline, after 3, 6, 12 24 and 36 months. Comparisons of percentage changes from baseline in strontium ranelate and placebo groups were performed with use of the Mann–Whitney test. Results were analysed on an intention-to-treat (ITT) basis.

Results: 5082 patients were included in this study (2536 receiving strontium ranelate 2 g/day and 2546 receiving a placebo).  In the strontium ranelate group, the bone resorption marker S-CTX decreased compared to the placebo group at every time point (all p<0.05) independently of age (below or over 80 years), familial history of osteoporosis (yes/no), body mass index (below or over 25kg/m²), or prevalent vertebral fracture (absence, 1, 2 or more). During the 2 first year of treatment, S-CTX is also decreased independently of addiction to smoking (yes/no). After 3 years of treatment the differences of S-CTX change between the placebo and the strontium ranelate groups varied between 4 and 15%, depending on the risk factor considered. In patients with family history of osteoporosis, after 3 years of follow-up, the between-group difference in S-CTX was 8.9%. In the same way, an increase in the bone formation markers PICP and BALP in women taking strontium ranelate compared to placebo was observed after 3 months and sustained during the 3 years independently of the presence of fracture risk factor in the study population (all p<0.05).

Conclusion:

During a 3-year treatment, strontium ranelate decreases bone resorption and stimulates bone formation in postmenopausal women independently of baseline osteoporosis risk factors. This effect is independent of the disease severity as demonstrated by a significant decrease in bone resorption markers and an increase in bone forming markers in patients with, no, 1 or 2 and more prevalent fracture.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/strontium-ranelate-uncouples-bone-resorption-from-bone-formation-in-osteoporotic-patients-with-or-without-clinical-risk-factors/