PAM17: IMPORTANT ISSUES IN NUMBER NEEDED TO TREAT ANALYSIS IN OSTEOPOROSIS TREATMENT

Abstract

Number Needed to Treat (NNT) is calculated in clinical trials by taking the inverse of the difference in absolute risk in the placebo group from the treatment group. It captures how many people would need to receive a treatment to prevent a disease or event. OBJECTIVES: To determine the roles of treatment efficacy and population characteristics in Number Needed to Treat (NNT) calculations within randomized clinical trials of osteoporosis pharmacological agents. METHODS: Data were collected from publications of three major clinical trials of pharmacological osteoporosis agents. Trials valuated were the Multiple Outcomes of Raloxifene Evaluation (MORE), Fracture Intervention Trial 1&2 (FIT) which evaluated Alendronate, and Vertebral Efficacy with Risedronate Therapy (VERT). NNT, mean age, baseline Bone Mineral Density (BMD) at spine, baseline vertebral fracture rate, vertebral fracture rates in the placebo and treatment groups, and relative risk reductions were abstracted. RESULTS: The Number Needed to Treat not only varied among different agents but also in different populations where the same treatment was used. The MORE trial reported two NNTs. The ?MORE 1? trial, where few participants had a prevalent vertebral fracture (11%), found an NNT of 46 while ?MORE 2?, where most participants had a prevalent vertebral fracture (88%), found an NNT of 16. FIT1, where all participants had prevalent vertebral fractures, reported an NNT of 15 while FIT2, no participants had a prevalent fracture, reported an NNT of 60. The VERT trial's NNT was calculated to be 20 using the above method. VERT had an 80% prevalent vertebral fracture rate. CONCLUSION: Variation in NNT is due to the different characteristics like placebo fracture rates as well as treatment efficacy. If one compares the trials with the most similar placebo group fracture rates, ?MORE2?, FIT1, and VERT, the Number Needed to Treat is quite similar. Dissimilar population characteristics as opposed to differences in treatment efficacy can be responsible for differences in NNT.