Combined therapy with lanthanum carbonate and calcium carbonate for hyperphosphatemia decreases serum FGF-23 level independently of calcium and PTH (COLC Study)

Background. Increased blood levels of fibroblast growth factor-23 (FGF-23) are associated with increased mortality. We evaluated the effect of combined therapy with lanthanum carbonate (LaC), a new phosphate binder and calcium carbonate (CaC) on serum levels of phosphate and FGF-23. Methods. This was a single-arm, open-label, multicenter study. Hemodialysis patients with a serum phosphate level >6.0 mg/dL despite CaC therapy were also given LaC for 16 weeks at a dose up to 2250 mg/day. CaC was given at a fixed dose throughout the 16-week period. Results. Of 42 patients enrolled, 36 completed the 16-week study. The serum phosphate level showed a significant decrease from 6.9 +/- 1.4 mg/dL at week 0 to 5.5 + 1.2 mg/dL at week 16 (-20.0%, P < 0.05). The median FGF-23 level showed a significant decrease from 8250 ng/L at week 0 to 5000 ng/L at week 16 (-39.2%, P < 0.05). In contrast, corrected serum calcium and the serum parathyroid hormone level showed no significant changes. A significant positive correlation (r = 0.442, P = 0.007) was demonstrated between the percent reduction of serum FGF-23 and that of serum phosphate. Conclusion. Both serum phosphate and FGF-23 levels were significantly decreased by treatment with LaC plus CaC.