Vertebral anti-fracture efficacy of strontium ranelate according to pre-treatment bone turnover.
Osteoporotic post-menopausal women patients in two randomised trials comparing the anti-fracture efficacy of strontium ranelate with placebo were separated into tertiles according to their baseline levels of biochemical markers of bone formation and resorption. The vertebral anti-fracture efficacy of strontium ranelate was shown to be independent of baseline bone turnover levels.


BACKGROUND
Bone turnover (BTO) levels vary among women at risk of osteoporotic fracture. Strontium ranelate is an anti-osteoporotic treatment increasing bone formation and reducing bone resorption. It was hypothesised that its anti-fracture efficacy would be independent of baseline BTO levels.


METHODS
Post-menopausal women with osteoporosis from two pooled studies were stratified in tertiles according to baseline levels of two BTO markers: bone-specific alkaline phosphatase (b-ALP, n = 4995) and serum C-telopeptide cross-links (sCTX, n = 4891). Vertebral fracture risk was assessed over 3 years with strontium ranelate 2 g/day or placebo.


RESULTS
In the placebo group, relative risk of vertebral fractures increased with BTO tertiles by 32% and 24% for patients in the highest tertile for b-ALP and CTX, respectively, compared to those in the lowest tertile. In the strontium ranelate group, incidences of vertebral fracture did not differ significantly across BTO tertiles. Significant reductions in vertebral fractures with strontium ranelate were seen in all tertiles of both markers, with relative risk reductions of 31% to 47% relative to placebo. Risk reduction did not differ among tertiles (b-ALP: p = 0.513; sCTX: p = 0.290).


CONCLUSIONS
The vertebral anti-fracture efficacy of strontium ranelate was independent of baseline BTO levels. Strontium ranelate offers clinical benefits to women across a wide range of metabolic states.
Collette
J
J
Department of Clinical Biology, Bone and Cartilage Markers Laboratory, University of Liège, Liège, Belgium. J.Collette@chu.ulg.ac.be
Bruyère
O
O
Kaufman
J M
JM
Lorenc
R
R
Felsenberg
D
D
Spector
T D
TD
Diaz-Curiel
M
M
Boonen
S
S
Reginster
J-Y
JY
D000368:Aged; D000369:Aged, 80 and over; D015519:Bone Density / Q000187:drug effects; D050071:Bone Density Conservation Agents / Q000627:therapeutic use*; D016723:Bone Remodeling / Q000502:physiology; D004311:Double-Blind Method; D005260:Female; D005272:Femur Neck / Q000503:physiopathology; D006801:Humans; D008159:Lumbar Vertebrae / Q000503:physiopathology; D008875:Middle Aged; D009942:Organometallic Compounds / Q000627:therapeutic use*; D015663:Osteoporosis, Postmenopausal / Q000150:complications / Q000188:drug therapy / Q000503:physiopathology; D058866:Osteoporotic Fractures / Q000517:prevention & control*; D016032:Randomized Controlled Trials as Topic; D016103:Spinal Fractures / Q000209:etiology / Q000517:prevention & control*; D013876:Thiophenes / Q000627:therapeutic use*; D016896:Treatment Outcome
D050071:Bone Density Conservation Agents; D009942:Organometallic Compounds; D013876:Thiophenes; C081587:strontium ranelate