#3641 DOES IBANDRONATE OR CALCIUM AND VITAMIN D MAINTAIN OR IMPROVE BONE MICROARCHITECTURE IN THE FIRST YEAR AFTER KIDNEY TRANSPLANTATION?

Abstract

Abstract Background and Aims Modern immunosuppressive protocols are associated with less loss of bone mass immediately after kidney transplantation, as compared with previous eras. Even so, bone microarchitecture may still be disturbed due to long-standing uremia, leading to bone fragility and fracture susceptibility. Trabecular bone score (TBS) is a new tool to assess trabecular bone microarchitecture based on standard dual energy X-ray absorptiometry (DXA) of lumbar spine images. TBS reflects bone quality rather than quantity. Studies on the effect of common anti-fracture strategies on TBS in kidney transplant recipients (KTR) are scarce. Our aim was to investigate different treatments on bone microarchitecture by TBS in KTR. Method We analyzed TBS changes and potential treatment effects in 179 de novo KTR, 118 of whom had participated in a randomized controlled trial[1] evaluating the effect of ibandronate (active/placebo) on top of calcium and vitamin D in the first year after kidney transplantation. Trial participants were compared to 61 patients transplanted in the same time-period, meeting the same study inclusion criteria, but receiving no specific bone-directed treatment. Correlations between changes in TBS and lumbar spine BMD were investigated. We used ANOVA and ANCOVA with adjustment for baseline TBS values to evaluate the potential effects of calcium and vitamin D with/without concomitant ibandronate on TBS 12 months after transplantation, as compared to no treatment. Results Mean TBS increased in all groups from baseline to 12 months after transplantation (2.1% for ibandronate/calcium/vitamin D, 2.7% for calcium/vitamin D, and 3.4% for no treatment). Adjusting for baseline TBS, there were no significant differences in TBS at 12 months, neither with overall comparison (p = 0.377) nor when comparing the groups pairwise. The correlation between TBS and BMD was weak (r = 0.170, p = 0.02) at baseline, and change in TBS was not significantly correlated with change in lumbar spine BMD in any of the groups. Conclusion In a group of de novo KTR with reasonably well-preserved bone mass, it does not appear that one year of treatment with ibandronate or calcium and vitamin D significantly affects bone quality as measured by TBS. We found surprisingly weak correlation between changes in TBS and BMD over the study period, indicating that these measurements reflect different aspects of bone integrity and metabolism. This study strengthens the view that focus should be on identifying KTR at high risk of fracture at time of transplantation, as these patients could benefit from anti-resorptive therapy.