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.