Objective: To evaluate the benefit of osteoporosis therapy with alendronate, estimating the number of patients necessary to treat to prevent a fracture (NNT) and the number of prevented fractures (NPF) by treating 100 patients.
Method: Analysis of different clinical scenarios from estimations of the incidence of osteoporotic fractures in western countries and the decrease in the relative risk of fracture obtained in recent clinical trials. Consideration was given to the influence of the possible post-therapy residual effects, life expectancy and functional impact of fractures.
Results: Results varied largely depending on the fracture risk of patients. Under the model assumptions, the NNT for hip fractures ranged from 7 (for women aged 80 with a bone mineral density [BMD] with Z < -2) to 333 (for women aged 50 with Z values ranging from 0 and -1). Thus, therapy of 100 women aged 80 years with a Z value < -2 for three years would prevent 14 hip fractures, 33 vertebral fractures and 8 wrist fractures. Therapy of 100 women aged 50-55 years with a Z value ranging from 0 to -1 would prevent 1 hip fracture, 2 vertebral fractures and 2 wrist fractures.
Conclusion: The proposed model allows for estimating the expected benefit for the different types of patients and underscores the relevance of concentrating therapeutic efforts in the groups of patients with the highest risk. On the other hand, it suggests that the obtained benefit when treating elderly female patients with low BMD is higher than that obtained with therapy during the years following menopause.