Gabapentin is effective in the treatment of cancer-related neuropathic pain: a prospective, open-label study.

BACKGROUND: Gabapentin has been evaluated in the treatment of nonmalignant neuropathic pain, however, there is little direct evidence evaluating its efficacy in cancer-related neuropathic pain. OBJECTIVE: This study evaluated the effectiveness of gabapentin to treat cancer-related neuropathic pain. DESIGN: This was an open-label study. Two parallel groups of patients were recruited with either treatment-related (radiotherapy, surgery, chemotherapy) or tumor-related neuropathic pain. Gabapentin was dose-escalated from 300 mg/d to 1.8 g/d. MEASUREMENTS: The primary outcome, pain, was assessed using the modified brief pain inventory. In addition patient descriptors of pain and scores of activities of daily living were collated together with demographic data. RESULTS: We recruited 62 patients with treatment-related (n = 25) or tumor-related (n = 37) neuropathic pain. There was a significant reduction in the worst, average, and current pain scores (p < 0.002), but not the least pain score (p = 0.21). Twenty-eight of 62 (45.2%) of patients achieved at least a one third reduction in pain score (95% confidence interval [CI] 32.5-58.3); the number needed to treat to obtain this benefit is 2.2 (95% CI 1.7-3.1). There was a significant reduction in all scores measuring the impact of pain on daily living (p < 0.003). There was no significant difference in pain scores at day 8 compared to day 15. Analysis of variance suggested that gender, but not etiology, or type of neuropathic pain, was a significant predictor of analgesic response and this warrants further investigation. CONCLUSION: We conclude that gabapentin is an effective treatment for cancer-related neuropathic pain.