Mineral Metabolism in Renal Transplant Recipients Discontinuing Cinacalcet at the Time of Transplantation: a Prospective Observational Study

Background: The calcimimetic cinacalcet is approved for treating secondary hyperparathyroidism in patients with chronic kidney disease on dialysis. Biochemical profiles and clinical outcomes in patients discontinuing cinacalcet at the time of transplantation are scarce.

Methods: We performed a prospective observational cohort study, including 303 incident renal transplant recipients, of whom 21 were on cinacalcet treatment at the time of transplantation. Parameters of mineral metabolism and incidence of parathyroidectomy and nephrocalcinosis in patients discontinuing cinacalcet at the time of transplantation patients ("cinacalcet +") were compared to cinacalcet-naïve patients ("cinacalcet -"). Mean follow-up was 35.6 ± 15.8 months.

Results: At the time of transplantation, parameters of mineral metabolism were similar in both groups. Conversely, at month 3, serum ionized calcium (p = 0.0007), calcitriol (p = 0.02), biointact parathyroid hormone (p = 0.06) levels and urinary fractional excretion of phosphorus (p = 0.06) were higher, while serum phosphorus levels (p = 0.06) were lower in "cinacalcet +." Analysis based on matching at the time of initiation showed that the course of post-transplant mineral metabolism in cinacalcet-treated patients (median treatment period 12.5 months) vs. cinacalcet-naïve patients was identical. "Cinacalcet +" patients are characterized by a high-incidence proportion of both post-transplant nephrocalcinosis (45% at month 3) and parathyroidectomy (28.6%). No difference in renal function was observed between "cinacalcet +" and "cinacalcet-" patients.

Conclusion: Cinacalcet does not affect the course of secondary hyperparathyroidism in patients awaiting kidney transplantation. Biochemical profiles and a high parathyroidectomy rate suggest rebound hyperparathyroidism in renal transplant recipients discontinuing cinacalcet at the time of transplantation, which may be related to the short exposure time specific to this population. Risk/benefit studies are urgently required to define the role of continued calcimimetic treatment in renal transplant recipients and to determine the optimal treatment of secondary hyperparathyroidism in patients listed for transplantation.