Ketamine Hydrochloride and Best Pain Management in Treating Cancer Patients With Neuropathic Pain

OBJECTIVES: Primary * To determine whether ketamine hydrochloride given in addition to best standard pain management improves malignant neuropathic pain compared to best standard pain management alone in patients with cancer. Secondary * To compare initial treatment benefit (at day 4 of assessment period of 16 days) using the sensory component of the McGill Short-Form Questionnaire. * To compare difference in overall pain between the study arms based on the pain-intensity visual-analogue score (VAS). * To compare difference in neuropathic pain between the study arms based on the Leeds Assessment of Neuropathic Symptoms and Signs (LANSS) pain scale. * To assess worst pain score (index neuropathic site) between the two arms. * To compare patient distress between the two arms based on NCCN Distress Thermometer. * To assess the side effects and tolerability of trial drug. * To assess the effect of intervention on quality of life scores (based on Euroqol thermometer), anxiety and depression (based on HADS), and opioid requirements. OUTLINE: This is a multicenter study. * Stage 1 (Run-in Period): Opioid doses are optimized, under a defined schedule, for up to a maximum of 10 days to ensure that all patients are on an optimized and stable regimen\* prior to randomization. Following the run-in-period, patients undergo reassessment. Patients who have improved pain scores (i.e., \< 4/10 on the visual-analogue score in the past 24 hours or \< 5 McGill Sensory Scale Score) are taken off the study. Patients whose scores have not improved continue on to Stage 2 of the study. NOTE: \*Stable regimen is defined as the same dose of controlled release and no more variation than 2 breakthrough opioid doses over the normal for that patient for a period of 48 hours. * Stage 2 (Titration Period): Patients are randomized to 1 of 2 treatment arms. * Arm I: Patients receive oral ketamine hydrochloride 4 times a day. Doses are titrated until when analgesia is achieved or individual side effects appear, for up to 14 days. * Arm II: Patients receive an oral placebo 4 times a day. Doses are titrated until when analgesia is achieved or individual side effects appear, for up to 14 days. * Stage 3 (Assessment Period): Patients receive the trial medication (i.e., ketamine hydrochloride or placebo) at the fixed optimum dose (reached during the titration period) for 16 days. Patients are allowed to receive breakthrough opioids at any time during the study. Patients complete quality-of-life and pain-assessment questionnaires periodically. Some patients may undergo blood sample collection periodically for pharmacogenomics studies at a later date. Peer Reviewed and Funded or Endorsed by Cancer Research UK.