Time to Benefit of Bisphosphonate Therapy for the Prevention of Fractures Among Postmenopausal Women With Osteoporosis: A Meta-analysis of Randomized Clinical Trials

IMPORTANCE The clinical decision to initiate bisphosphonate therapy for the treatment of osteoporosis requires balancing shorter-term harms and burdens (eg, gastroesophageal irritation or severe musculoskeletal pain) with longer-term benefits in reducing potential fractures. OBJECTIVE To assess the time to benefit (TTB) of bisphosphonate therapy for the prevention of nonvertebral and other fractures among postmenopausal women with osteoporosis. DATA SOURCES Randomized clinical trials (RCTs) were identified from systematic reviews commissioned by the US Preventive Services Task Force (1 review), the Agency for Healthcare Research and Quality (1 review), the Cochrane Library (2 reviews), and the Endocrine Society (1 review). STUDY SELECTION Studies selected were RCTs involving postmenopausal women with a diagnosis of osteoporosis based on existing vertebral fractures or bone mineral density T scores of -2.5 or lower. The selection process was focused on studies of alendronate, risedronate, and zoledronic acid because they are guideline-recommended first-line agents for reducing nonvertebral fractures. Studies were excluded if they did not focus on women with a primary diagnosis of osteoporosis, had no placebo arm, or had a lack of data on time to fracture. DATA EXTRACTION AND SYNTHESIS Random-effects Weibull survival curves were fitted and Markov chain Monte Carlo methods were used to estimate the absolute risk reduction (ARR) and TTB for each study. These estimates were pooled using a random-effects meta-analysis model. MAIN OUTCOMES AND MEASURES The primary outcome was the time to 3 different ARR thresholds (0.002, 0.005, and 0.010) for the first nonvertebral fracture. Secondary outcomes included the time to 4 ARR thresholds (0.001, 0.002, 0.005, and 0.010) for hip fracture, any clinical fracture, and clinical vertebral fracture. RESULTS Of 67 full-text articles identified, 10 RCTs comprising 23 384 postmenopausal women with osteoporosis were included either as the original RCT or part of subsequently published pooled analyses. Among the studies, the number of participants ranged from 994 to 7765, with mean (SD) age ranging from 63 (7) years to 74 (3) years and follow-up duration ranging from 12 to 48 months. The pooled meta-analysis found that 12.4 months (95% CI, 6.3-18.4 months) were needed to avoid 1 nonvertebral fracture per 100 postmenopausal women receiving bisphosphonate therapy at an ARRof0.010. To prevent 1 hip fracture, 200 postmenopausal women with osteoporosis would need to receive bisphosphonate therapy for 20.3 months (95% CI, 11.0-29.7 months) at an ARR of 0.005. In addition, 200 postmenopausal women with osteoporosis would need to receive bisphosphonate therapy for 12.1 months (95% CI, 6.4-17.8 months) to avoid 1 clinical vertebral fracture at an ARR of 0.005. CONCLUSIONS AND RELEVANCE This meta-analysis found that the TTB of bisphosphonate therapy was 12.4 months to prevent 1 nonvertebral fracture per 100 postmenopausal women with osteoporosis. These results suggest that bisphosphonate therapy is most likely to benefit postmenopausal women with osteoporosis who have a life expectancy greater than 12.4 months.