Randomized trial of effect of alendronate continuation versus discontinuation in women with low BMD: results from the Fracture Intervention Trial long-term extension

Abstract

To determine the effects of continuation versus discontinuation of alendronate on BMD and markers of bone turnover, we conducted an extension trial in which 1099 older women who received alendronate in the FIT were re-randomized to alendronate or placebo. Compared with women who stopped alendronate, those continuing alendronate for 3 years maintained a higher BMD and greater reduction of bone turnover, showing benefit of continued treatment. However, among women who discontinued alendronate and took placebo in the extension, BMD remained higher, and reduction in bone turnover was greater than values at FIT baseline, showing persistence of alendronate's effects on bone.

Introduction: Prior trials including the Fracture Intervention Trial (FIT) have found that therapy with alendronate increases BMD and decreases fracture risk for up to 4 years in postmenopausal women with low BMD. However, it is uncertain whether further therapy with alendronate results in preservation or further gains in BMD and if skeletal effects of alendronate continue after treatment is stopped.

Materials and methods: We conducted a follow-up placebo-controlled extension trial to FIT (FIT long-term extension [FLEX]) in which 1099 women 60-86 years of age who were assigned to alendronate in FIT with an average duration of use of 5 years were re-randomized for an additional 5 years to alendronate or placebo. The results of a preplanned interim analysis at 3 years are reported herein. Participants were re-randomized to alendronate 10 mg/day (30%), alendronate 5 mg/day (30%), or placebo (40%). All participants were encouraged to take a calcium (500 mg/day) and vitamin D (250 IU/day) supplement. The primary outcome was change in total hip BMD. Secondary endpoints included change in lumbar spine BMD and change in markers of bone turnover (bone-specific alkaline phosphatase and urinary type I collagen cross-linked N-telopeptide).

Results: Among the women who had prior alendronate therapy in FIT, further therapy with alendronate (5 and 10 mg groups combined) for 3 years compared with placebo maintained BMD at the hip (2.0% difference; 95% CI, 1.6-2.5%) and further increased BMD at the spine (2.5% difference; 95% CI, 1.9-3. 1%). Markers of bone turnover increased among women discontinuing alendronate, whereas they remained stable in women continuing alendronate. Cumulative increases in BMD at the hip and spine and reductions in bone turnover from 8.6 years earlier at FIT baseline were greater for women continuing alendronate compared with those discontinuing alendronate. However, among women discontinuing alendronate and taking placebo in the extension, BMD remained higher and reduction in bone turnover was greater than values at FIT baseline.

Conclusions: Compared with women who stopped alendronate after an average of 5 years, those continuing alendronate maintained a higher BMD and greater reduction of bone turnover, showing benefit of continued alendronate treatment on BMD and bone turnover. On discontinuation of alendronate therapy, rates of change in BMD at the hip and spine resumed at the background rate, but discontinuation did not result in either accelerated bone loss or a marked increase in bone turnover, showing persistence of alendronate's effects on bone. Data on the effect of continuation versus discontinuation on fracture risk are needed before making definitive recommendations regarding the optimal length of alendronate treatment.