Bisphosphonate Use after Kidney Transplantation Is Associated with Lower Fracture Risk.

Key points: Bisphosponate use may decrease the risk of fracture in patients receiving kidney transplant. Identifying those at risk of fracture after kidney transplant is critical.

Background: Kidney transplant recipients are at higher risk of fractures compared with the general population. The use of bisphosphonates has been shown to increase bone mineral density after transplantation but has not been shown to lower fracture rates. In this study, we aim to determine whether exposure to bisphosphonates is associated with lower incidence of nonvertebral fractures after kidney transplantation.

Methods: We conducted a retrospective review for all Southern California Kaiser Permanente kidney transplant recipients with osteoporosis transplanted between 2000 and 2019. Baseline variables were collected. Those prescribed an oral bisphosphonate were compared with those who were not. The primary outcome was nonvertebral fracture. Chi-square test was used to evaluate categorical variables and Wilcoxon rank-sum test for continuous variables. Propensity scores were generated to balance covariates in the bisphosphonate and nonbisphosphonate groups. Cause-specific hazard and subdistribution (Fine-Gray) methods were performed for competing risk analysis. Death-censored graft survival was evaluated as a secondary outcome using standard Cox regression.

Results: There were 489 patients included in the study, 203 of which were in the bisphosphonate group. The cause-specific hazard model suggested a 64% lower risk of nonvertebral fracture in the bisphosphonate group ( P = 0.02). The Fine-Gray hazard model treating death as a competing risk did not show lower relative incidence of nonvertebral fracture. Bisphosphonate treatment was associated with lower death-censored graft failure ( P = 0.002).

Conclusions: Bisphosphonate use after kidney transplantation may be associated with a lower risk of nonvertebral fracture after transplant. Bisphosphonate use in this study was also associated with lower death-censored graft failure. Caution is advised when interpreting these results given the retrospective nature of the study.