A Pilot Trial of Intravenous Pamidronate for Low Back Pain

INTRODUCTION Pamidronate and other bisphosphonates (bisph) have an anti-nociceptive effect in animals. In humans, IV pamidronate is analgesic in patients affected by numerous painful conditions, including cancer bone pain, complex regional pain syndrome (CRPS), ankylosing spondylitis, and rheumatoid arthritis. The investigators have explored the effect of IV pamidronate in the management of chronic low back pain (CLBP), a worldwide public health problem in terms of lost workdays, treatment costs, and suffering.

The study was a randomized, double blind, dose-escalation trial of IV pamidronate. Study participants were divided among four study phases. Each group received IV placebo or escalating doses of IV pamidronate.

STUDY DESIGN A phase I-II, randomized, double-blind, placebo controlled, dose finding study for the treatment of patients with CLBP with IV pamidronate. The study was first conducted at Beth Israel Medical Center, NY for the first two groups, and was completed at Mount Sinai Medical Center , NY for the remaining groups.

PRIMARY OBJECTIVES The intent of this pilot study was to determine the optimal IV pamidronate treatment protocol for CLBP in a Phase III trial. Primary study aims were safety and average daily pain. Subjects used an electronic diary (LOGPAD) to record their daily adverse events (AEs) and their baseline and post-treatment average pain on the 0-10 numerical rating scale (NRS).

STATISTICAL ANALYSES All the analysis were performed on an intention-to-treat basis. Primary outcomes are LOGPAD change in pain severity and whether a patient was a responder (pain score dropped ≥2 points or ≥30%). Because there was no statistical difference in these two outcomes among the 4 placebo groups, all placebo patients were combined (Comb PL) in the subsequent analyses. Primary analytic tool was mixed model for repeated measures (MMRM), assuming autoregressive covariance structure (LOGPAD pain and Brief Pain Inventory - BPI interferences), and Generalized Estimating Equation (GEE) model for categorical outcomes (Response rates and Patient Global Impression of Change - PGIC). The main objective was to assess whether the changes in outcome from baseline or the response rates were the same across the study phases, while adjusting for baseline values and time effect. Least square means were contrasted. Interaction between time and study phases were also tested to see if the treatment effect is a function of time. Fisher's exact tests or ANOVA (Kruskal-Wallis) tests were performed for cross-sectional group comparison, including baseline.