Bone density after teriparatide in patients with or without prior antiresorptive treatment: one-year results from the EUROFORS study

Objective: Recombinant teriparatide, a bone anabolic agent, is given to treatment-naive and pre-treated patients with severe osteoporosis, but few data exist comparing the response to teriparatide in these groups. EUROFORS (the EUROpean study of FORSteo double dagger) enrolled postmenopausal women with established osteoporosis who were either treatment-naive or had prior antiresorptive (AR) treatment with or without documented inadequate clinical response. The objective of the secondary analysis described here was to evaluate the interim bone mineral density (BMD) response in these groups after one year of open-label teriparatide therapy. Research design and methods: Postmenopausal women with established osteoporosis who enrolled in a prospective, randomized, controlled trial received open-label teriparatide 20 mu g/day for the first year. With respect to their prior osteoporosis treatment history, they were retrospectively allocated to one of three groups: treatment-naive (n = 204), prior treatment with an antiresorptive drug (AR-pretreated) (n = 240), or prior antiresorptive treatment with inadequate response (inadequate AR-responders) (n = 421). BMD was measured by dual energy x-ray absorptiometry. Results: Lumbar spine BMD increased from baseline (p < 0.001) in the three groups (mean, 95% CI); treatment-naive: 8.4% (7.4%, 9.3%); AR-pretreated: 7.1% (6.3%, 7.9%); inadequate AR-responders: 6.2% (5.6%, 6.9%). Total hip BMD increased from baseline in the treatment-naive (p < 0.001): 1.8% (1.1%, 2.5%) but did not change in the AR-pretreated: 0.4% (-0.2%, 1.1%) or inadequate AR-responders: -0.3% (-0.9%, 0.2%). Treatment-emergent adverse events were similar in the three groups. Conclusion: One year of teriparatide significantly (p < 0.001) increased spine BMD in all groups, and total hip BMD in the treatment-naive group. Because of the limitations of this interim analysis (most importantly, the short duration of treatment and lack of a control group), further study is needed to determine the optimal treatment duration to reach the potential BMD gains at the proximal femur in patients with prior antiresorptive drug use (mostly bisphosphonates).