Effect of alendronate on vertebral fracture risk in women with bone mineral density T scores of-1.6 to -2.5 at the femoral neck: the Fracture Intervention Trial

Abstract

Objectives: To determine the efficacy of alendronate treatment on risk of vertebral fracture in a subgroup of women from the Fracture Intervention Trial who had bone mineral density T scores between -1.6 and -2.5 at the femoral neck and to describe how soon after initiation of therapy alendronate becomes effective and whether it is consistent in women with and without existing radiographic vertebral fracture.

Patients and methods: From May 1992 to March 1997, postmenopausal women aged 55 to 80 years were randomized to receive alendronate at 5 mg/d for 2 years and 10 mg/d thereafter or placebo for up to 4.5 years (mean, 3.8 years) in a controlled, double-blind, multicenter study.

Results: A total of 3737 postmenopausal women were included in the study, 1878 in the alendronate group and 1859 in the placebo group. Risk of vertebral fracture was significantly reduced by alendronate compared with placebo for clinical (relative risk [RR], 0.40; 95% confidence interval [CI], 0.19-0.76; P=.005) and radiographic (RR, 0.57; 95% CI, 0.41-0.81; P=-.002) fracture. The reductions in vertebral fracture risk were consistent in women with and without an existing radiographic vertebral fracture for clinical (RR, 0.34; 95% CI, 0.12-0.84; and RR, 0.46; 95% CI, 0.16-1.17; respectively) and radiographic (RR, 0.53; 95% CI, 0.34-0.82; and RR, 0.64; 95% CI, 0.38-1.10; respectively) fractures. In both groups, the effect of alendronate on clinical vertebral fracture was noted soon after therapy was initiated. The absolute risk of vertebral fracture was low in women without a baseline radiographic fracture.

Conclusions: In women with low bone mass who do not meet the bone mineral density criterion for osteoporosis, alendronate is effective in reducing the risk of vertebral fractures. The absolute benefit of this therapy in women with a T score between -1.6 and -2.5 is greater in women with an existing vertebral fracture and/or with other risk factors. The effect of alendronate occurs early.