Early changes in serum N-telopeptide and C-telopeptide cross-linked collagen type 1 predict long-term response to alendronate therapy in elderly women

The aim of this study was to determine whether early changes in serum marke rs of bone resorption could predict long-term responses. in bone mineral de nsity (BMD) after alendronate therapy in elderly women. One hundred and twe nty women (mean age, 70 yr) were randomized to alendronate or placebo in th is double blind, placebo-controlled clinical trial for 2.5 yr. Outcome meas ures were hip and spine BMD and biochemical markers of bone resorption, inc luding serum N-telopeptide and C-telopeptide cross-linked collagen type I ( NTx and CTx, respectively). Serum NTx and CTx were highly correlated at bas eline (r = 0.73; P < 0.001) and remained so throughout the study (range, r = 0.36-0.56; all P < 0.05). After treatment with alendronate, serum NTx dec reased 30.4 +/- 16.0% at 6 months, reaching a nadir of -36.7 +/- 18.0% by 2 4 months (P < 0.001). Serum CTx decreased 43.5 +/- 67.0% at 6 months and co ntinued to decrease to 67.3 +/- 19.3% at 2.5 yr (P < 0.001). Moreover, decr eases in serum NTx and CTx at 6 months were correlated with long-term impro vements in vertebral BMD at 2.5 yr in patients receiving alendronate therap y (NTx: r = -0.42; CTx: r = -0.31; both P < 0.05). We conclude that early c hanges in serum NTx and CTx, markers of bone resorption, predict long-term changes in vertebral BMD in elderly women receiving alendronate therapy and provide a useful tool to assess skeletal health.