Relationship between 3-month changes in biochemical markers of bone remodelling and changes in bone mineral density and fracture incidence in patients treated with strontium ranelate for 3 years

From two randomised controlled trials, it is shown that 3-month changes in biochemical markers of bone formation (bone-specific alkaline phosphatase and C-terminal propeptide of type I procollagen) were associated with 3-year bone mineral density (BMD) changes, but not fracture incidence in patients treated with strontium ranelate. The purpose of this study was to assess if short-term change in biochemical markers of bone remodelling is associated with long-term BMD change and fracture incidence observed during treatment with strontium ranelate. From the SOTI and TROPOS trials, bone-specific alkaline phosphatase (BALP), C-terminal propeptide of type I procollagen (PICP), serum C-terminal telopeptides (S-CTX) and urine N-terminal telopeptides of type I collagen (U-NTX) were assessed at baseline and after 3 months. Two thousand three hundred seventy-three women were included in this study. Multiple regression analysis showed that 3-month changes in PICP and BALP but not s-CTX I nor s-NTX I were significantly (p < 0.001) associated with 3-year BMD changes at the lumbar spine and the femoral neck. Changes in s-CTX I, PICP and BALP were significantly associated with change in total proximal femur BMD. Changes in biochemical markers explain less than 8% of the BMD changes. The 3-month changes in BALP, PICP s-CTX I and s-NTX I were not significantly associated with fracture incidence. Short-term changes in biochemical markers of bone formation are associated with future BMD changes in patients treated with strontium ranelate, suggesting a bone-forming activity of this treatment, but are not appropriate to monitor the efficacy of strontium ranelate at the individual level.