[Analysis of the efficacy and factors influencing the response of secondary hyperparathyroidism patients on hemodialysis to cinacalcet].

BACKGROUND: Treatment of secondary hyperparathyroidism with cinacalcet improves control of PTH, phosphorus, calcium and Ca x P product, enabling to achieve targets recommended by K/DOQI guidelines for PTHi in only 30-50% of patients, in studies with a very selected population. The aim of this study was to analyze its effectiveness in real clinical practice, comparing results with targets recommended by K/DOQI and KDIGO guidelines and to investigate factors having influence on PTH responsiveness to cinacalcet.

METHODS: We collected data of evolution of 74 patients on hemodialysis with secondary hyperparathyroidism who were treated with cinacalcet for at least 6 months.

RESULTS: According K/DOQI targets we observed a reduction of proportion of patients with PTHi > 300 pg/ml to 50%, a decrease of hyperphosphoremia from 38.4% to 23.3% and proportion of patients with Ca x P product > 55 mg2/dl2 from 37.8% to 15.1%. By contrast, presence of hypocalcemia increases from 2.7% to 12.3%. Comparing with KDIGO targets, proportion of patients with PTHi > 600 pg/ml decreased from 41.1% to 16.4% and with hyperphosphoremia from 68.5% to 52.1%. However, when considering patients with baseline PTHi > 600 pg/ml prevalence of P > 4.5 mg/dl decreased from 83.3% to 55.2%. We observed significant changes of phosphate binders after cinacalcet treatment with an increase in calcium carbonate doses (pre 0.61 +/- 1.53 g of calcium/day vs post-cinacalcet 0.95 +/- 1.98 g of calcium/day; p = 0.03) that was prescribed to prevent hypocalcemia and not as phosphate binder. Responsiveness were lower in patients who were taking higher doses of sevelamer at baseline, showing at the end of the study higher PTHi (no-sevelamer: 312 +/- 245 pg/ml; sevelamer < 6.4 g/day: 510 +/- 490 pg/ml; sevelamer > 6.4 g/day: 526 +/- 393 pg/ml; p = 0.04) and phosphorus (no-sevelamer: 4.5 +/- 1.2 mg/dl; sevelamer < 6.4 g/day: 4.2 +/- 1.5 mg/dl; sevelamer > 6.4 g/day: 5.7 +/- 0.9 mg/dl; p=0.01) serum levels. Use of paricalcitol did not show any influence on PTH response. Patients achieving targets for PTH at the end of the study showed a good response early, with a significant decrease of PTHi levels at three months (159 +/- 84 vs 630 +/- 377 pg/ml; p < 0.001) with significantly lower doses of cinacalcet (33.8 +/- 22.5 vs 51.1 +/- 25.1 mg/day; p = 0.003). Using multivariate analysis we found that percent of PTHi reduction was related with baseline PTHi levels and taking sevelamer as phosphate binder at baseline.

CONCLUSION: Use of cinacalcet improves grade of control of secondary hyperparathyroidism in non-selected patients in hemodialysis, showing poor response in population with higher PTHi levels and who takes higher doses of sevelamer at baseline. By contrast, a reduction of PTHi levels at 3 months of treatment with relatively lower doses is a pronostic marker of good response to cinacalcet treatment.