Monitoring of alendronate treatment and prediction of effect on bone mass by biochemical markers in the early postmenopausal intervention cohort study

To establish whether biochemical markers could be used to monitor alendrona te (ALN) treatment and predict long-term response in bone mass, we used res ults from an ongoing, randomized trial of ALN treatment for prevention of p ostmenopausal osteoporosis (n = 1202). In women treated with ALN (5 mg), ch ange from baseline at month 6 in urine N-telopeptide cross-links of type I collagen (NTX) and osteocalcin (OC) correlated with change from baseline at month 24 in spine, hip, and total body bone mineral density (BMD) [r = -0. 28 to -0.31(NTX) and r = -0.16 to -0.25 (OC), P < 0.001]. This corresponded to a 4- to 5-fold greater increase at month 24 in BMD in the tertiles, wit h the greatest decrease at month 6 in NTX or OC. In women treated with ALN (5 mg) who had a change at month 24 in spine BMD of at least 0%, 86% (NTX) and 79% (OC) had a decrease at month 6 of at least 40% (NTX) or 20% (OC) (s ensitivity). The corresponding specificities were 48% (NTX) and 53% (OC). I n conclusion, change at month 6 in NTX and OC, in groups of women treated w ith ALN, indicated the numeric long-term response in BMD within these group s. In individual women, a decrease at month 6, in NTX or OC below the cut-p oint, validly identified women who responded, on ALN treatment, with a stab ilization or an increase in bone mass. However, lack of decrease below the cut-point in NTX or OC could not be used to identify women with a bone loss during ALN treatment.