Sustained vertebral antifracture efficacy of oral anti-osteoporotic therapies in postmenopausal osteoporosis

Objective: Vertebral fractures are common in women with postmenopausal osteoporosis, a chronic condition requiring long-term treatment with anti-osteoporotic treatments. Therefore, it is important to assess sustainability of antifracture efficacy. Methods: A review of the literature to determine pivotal vertebral fracture studies for oral bisphosphonates (ibandronate, risedronate and alendronate), strontium ranelate, and raloxifene and to evaluate vertebral antifracture efficacy over time. Results: Data from the BONE trial showed that ibandronate sustained vertebral antifracture efficacy over time (58% vertebral fracture risk reduction in first year p = 0.0561, increased to 62% for years 0-3; p < 0.001). The Vertebral Efficacy with Risedronate Therapy-North America (VERT-NA) and VERT-multi-national (VERT-MN) studies demonstrated that the relative risk reduction (RRR) with risedronate versus placebo decreased over time (VERT-NA: 65% for first year to 41% for years 0-3; VERT-MN: 61% for first year to 49% for years 0-3). Data from the Fracture Intervention Trial (FIT) I trial with alendronate showed that the RRR in the cumulative incidence of new vertebral fractures versus placebo decreased from 62% for years 0-2 to 47% for years 0-3. Similar decreases in RRR over time were reported with strontium ranelate in the Spinal Osteoporosis Therapeutic Intervention study (SOTI; 49% for first year to 33% for years 0-4) and Treatment of Peripheral Osteoporosis Study (TROPOS; 45% for first year to 24% for years 0-5). No clear trend exists for sustained efficacy over time with raloxifene. Conclusions: Vertebral fracture protection could be interpreted to decrease over time with alendronate, risedronate and strontium ranelate, and may be due to multiple factors. Ibandronate sustained vertebral antifracture efficacy over time.