Drugs for osteoporosis: time to reach fracture risk reduction varies

Most patients on anti-osteoporotic therapy achieve a reduced fracture risk on long-term treatment, but the time this takes may differ for each drug. After 2 years, more teriparatide-treated patients reached the surrogate threshold effect (STE) than patients on denosumab or bisphosphonates.

Bone mineral density (BMD) STE is described as the minimally necessary treatment effect on BMD that is predictive of reduced fracture risk with 95% certainty [1]. Dr Giovanni Adami (University of Verona, Italy) explained that the necessary thresholds were recently validated and found different, depending on the type of fracture intended to be reduced in risk [1,2]. The STE estimates for any minimum fracture risk reduction for all, vertebral, hip, and nonvertebral fractures were determined at 1.83%, 1.42%, 3.18%, and 2.13% [2].

The current study used longitudinal information from the DeFRA database between 2012 and 2022 [1]. It identified 1,523 women at high risk of fracture starting therapy with bisphosphonates, 390 with denosumab, and 104 with teriparatide. The mean age of this cohort was 68.2, 10-year major osteoporotic fracture risk was 15.7%, and the median follow-up time was 826 days.

Regarding the rates of patients reaching STE after 2 years of treatment, the proportions varied according to the treatment (see Table), type of fracture, and amount of risk reduction. Regarding all fractures, any risk reduction was achieved by 24.2% (bisphosphonates), 48.5% (denosumab), and 62.9% (teriparatide) at this time point. The respective proportions were 24.4%, 49.1%, and 62.9% for vertebral fractures and 21.4%, 46.9%, and 61.4% for hip fractures, respectively. Kaplan-Meier curves that estimated the likelihood of attaining a T-score higher than -2.5 differed according to treatment. For example, a patient with a T-score of -3.0 at baseline demonstrated a 35% chance of reaching osteopenic levels after 2 years on bisphosphonates but a 54% or 60% chance on denosumab or teriparatide.

“In the long term, if you follow up the patients for over 6 years, you will find that approximately 100% of patients with denosumab and 80% of patients on bisphosphonates reach the STE,” Dr Adami underlined in his conclusion.

Table: Percentage of patients reaching various STEs, stratified by treatment, at 2 years [1]


STE, surrogate threshold effect.

1. Adami Proportion of patients reaching the bone mineral density (BMD) surrogate threshold effect (STE) with bisphosphonates, denosumab and teriparatide. OP0242, EULAR 2023, 31 May–3 June, Milan, Italy.
2. Eastell R, et J Bone Miner Res. 2022;37:29-35.

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Posted on 31 July, 202331 July, 2023