Effects of bisphosphonates on long-term kidney transplantation outcomes

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.

Impact of bisphosphonate treatment on bone mineral density after kidney transplant

BACKGROUND

Mineral bone disease is associated with chronic kidney disease and persists after kidney transplantation. Immunosuppressive treatment contributes to the pathogenesis of this disease. Bisphosphonate treatments have shown positive but indefinite results.

AIM

To evaluate the effectiveness and safety of bisphosphonate treatment on post kidney transplantation bone mineral density (BMD).

METHODS

We included kidney transplant recipients (KTRs) whose BMD was measured after the operation but before the initiation of treatment and their BMD was measured at least one year later. We also evaluated the BMD of KTRs using two valid measurements after transplantation who received no treatment (control group).

RESULTS

Out of 254 KTRs, 62 (39 men) were included in the study. Bisphosphonates were initiated in 35 KTRs in total (20 men), 1.1 ± 2.4 years after operation and for a period of 3.9 ± 2.3 years while 27 (19 men) received no treatment. BMD improved significantly in KTRs who received bisphosphonate treatments (from -2.29 ± 1.07 to -1.66 ± 1.09, P < 0.0001). The control group showed a non-significant decrease in BMD after 4.2 ± 1.4 years of follow-up after surgery. Kidney function was not affected by bisphosphonate treatment. In KTRs with established osteoporosis, active treatment had a similar and significant effect on those with osteopenia or normal bone mass.

CONCLUSION

In this retrospective study of KTRs receiving bisphosphonate treatment, we showed that active treatment is effective in preventing bone loss irrespective of baseline BMD.

New Human Leukocyte Antigen (HLA) Antibody Formation and Creatinine Elevation With Abaloparatide in Kidney Transplant Recipient

A 39-year-old female with a history of kidney transplant presented to the endocrinology clinic for osteoporosis evaluation after sustaining an ankle fracture from a fall. Her kidney transplant regimen (mycophenolate mofetil 360 mg twice a day, tacrolimus 0.5 mg every morning and 0.5-1 mg every evening, prednisone 5 mg/day) and baseline creatinine (1.0-1.2 mg/dL) had been stable for several years. After an appropriate secondary workup, she was started on abaloparatide 80 μg subcutaneous daily injections for osteoporosis. She had a good initial biochemical response to therapy. However, 5 months after abaloparatide initiation she was found to have a new elevation in serum creatinine (1.17 to 1.69 mg/dL) despite stable serum tacrolimus trough levels, and two new human leukocyte antigen (HLA) antibodies (anti-HLA antibodies detected to Cw7 and DP28). Abaloparatide was stopped due to concern for immunogenicity. There was no evidence of rejection on kidney biopsy and she was restabilized on her transplant regimen with a new baseline creatinine of 1.3-1.6 mg/dL. The patient was subsequently started on teriparatide 20 μg daily subcutaneous injections for 2 years with good biochemical response, significant improvement in bone mineral density, and stable transplant regimen without additional signs of immunogenicity or rejection. This is the first case report to raise concern about immunogenicity with abaloparatide in solid organ transplant recipients. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Management of osteoporosis in patients with chronic kidney disease

Patients with CKD have a 4-fivefold higher rate of fractures. The incidence of fractures increases with deterioration of kidney function. The process of skeletal changes in CKD patients is characterized by compromised bone strength because of deterioration of bone quantity and/or quality. The fractures lead to a deleterious effect on the quality of life and higher mortality in patients with CKD. The pathogenesis of bone loss and fracture is complex and multi-factorial. Renal osteodystrophy, uremic milieu, drugs, and systemic diseases that lead to renal failure all contribute to bone damage in CKD patients. There is no consensus on the optimal diagnostic method of compromised bone assessment in patients with CKD. Bone quantity and mass can be assessed by dual-energy x-ray absorptiometry (DXA) or quantitative computed tomography (QCT). Bone quality on the other side can be assessed by non-invasive methods such as trabecular bone score (TBS), high-resolution bone imaging methods, and invasive bone biopsy. Bone turnover markers can reflect bone remodeling, but some of them are retained by kidneys. Understanding the mechanism of bone loss is pivotal in preventing fracture in patients with CKD. Several non-pharmacological and therapeutic interventions have been reported to improve bone health. Controlling laboratory abnormalities of CKD-MBD is crucial. Anti-resorptive therapies are effective in improving BMD and reducing fracture risk, but there are uncertainties about safety and efficacy especially in advanced CKD patients. Accepting the prevalent of low bone turnover in patients with advanced CKD, the osteo-anabolics are possibly promising. Parathyroidectomy should be considered a last resort for intractable cases of renal hyperparathyroidism. There is a wide unacceptable gap in osteoporosis management in patients with CKD. This article is focusing on the updated management of CKD-MBD and osteoporosis in CKD patients. Chronic kidney disease deteriorates bone quality and quantity. The mechanism of bone loss mainly determines pharmacological treatment. DXA and QCT provide information about bone quantity, but assessing bone quality, by TBS, high-resolution bone imaging, invasive bone biopsy, and bone turnover markers, can guide us about the mechanism of bone loss.