NEW YORK (Reuters Health)—After discontinuation of teriparatide, increases in bone mineral density (BMD) are greater with denosumab than with zoledronic acid, but whether that translates into a decreased fragility fracture risk remains unknown, researchers say.
Teriparatide was the first anabolic treatment approved for osteoporosis in the U.S. It has been shown to increase BMD, and that increase has been associated with a decreased risk of fractures. However, because it also has been associated with osteosarcoma, treatment is limited to two years, after which antiresorptive therapy is required to limit BMD loss.
Dr. David Burkhard of Michigan State University College of Human Medicine in Grand Rapids and colleagues reviewed data on 64 patients who completed teriparatide treatment and compared the effects of denosumab versus zoledronic acid or no treatment on BMD and bone turnover markers.
As reported online March 14 in Osteoporosis International, patients who were started on denosumab showed the largest increase in BMD after two years of antiresorptive treatment, whereas patients who discontinued osteoporosis treatment experienced a significant decline in BMD.
Specifically, at the lumbar spine, denosumab demonstrated a significantly greater increase in BMD (5.68 +/-6.7%) compared to no antiresorptive therapy (− 1.56 +/- 7.7%, p = 0.032).
By contrast, no significant change in BMD was seen with zoledronic acid (1.75 +/- 4.1%) compared with denosumab or no antiresorptive therapy.
At the femoral neck, denosumab significantly increased BMD (4.94 +/- 8.2%) compared to no antiresorptive therapy (− 1.12 +/- 4.2%) or zoledronic acid (− 1.05 +/- 4.0%).
The change in BMD was similar with zoledronic acid and no antiresorptive treatment.
All three groups had significant declines in bone turnover markers CTX and P1NP after two years of antiresorptive or no therapy, but no significant between-group differences emerged.
The authors note that because zoledronic acid has a persistent effect and denosumab does not, patients treated with denosumab need closer followup to ensure they stay on treatment. Also, they state, “Although BMD increases were greater with denosumab than with zoledronic acid, it is not known if this will result in greater reduction of fractures.”
Dr. Burkhard told Reuters Health by email, “Our study… backs up many other studies in the literature that show the importance of treating osteoporosis.”
Because osteoporosis can be treated by so many different types of doctors, “there isn’t always that sense of responsibility to start patients on an osteoporosis drug because it’s not always clear whose responsibility that is,” he said. “Luckily, in the city where I practice, there is a bone health clinic that all patients with fragility fractures get directly referred to for treatment management. Not all cities are this lucky.”