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

Background: Kidney transplant recipients are at higher risk of fractures compared to 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. Here, we aim to determine if exposure to bisphosphonates associates with lower incidence of non-vertebral 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 to those who were not. The primary outcome was non-vertebral fracture. Chi square was used to evaluate categorical variables and Wilcoxson rank sum test for continuous variables. Propensity scores were generated to balance covariates in the bisphosphonate and non-bisphosphonate groups. Cause-specific hazard and sub distribution (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 non-vertebral 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 non-vertebral fracture. Bisphosphonate treatment was associated with lower death censored graft failure (p=0.002).

Conclusions: Bisphosphonate use after kidney transplantation may associate with lower risk of non-vertebral 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.