Evaluation of Dronabinol to Decrease Opioid Use for Cancer-Induced Bone Pain

BACKGROUND: Bone metastases (BM) from breast cancer cause significant cancer-induced bone pain (CIBP). Management of CIBP is primarily with opioids, which have notable side effects. In preclinical models, cannabinoid receptor (CB)2 and CB1 agonists were shown to decrease CIBP and bone degradation. We hypothesized that the addition of CB2/CB1 agonists would decrease opioid requirements in patients with BM. METHODS: We conducted a single-arm study among breast cancer patients with BM on opioid therapy. Patients were treated with 10 mg dronabinol BID for 8 weeks. Our primary objective was to determine the proportion who decreased their opioid use by ≥ 20%. Participants completed the Brief Pain Inventory and the European Organization for Research and Treatment of Cancer quality of life questionnaires before and after treatment. Pre- and post-treatment blood and urine were collected for analysis of biomarkers of bone remodeling. RESULTS: We enrolled 14 evaluable patients, and 4 decreased opioid use by ≥ 20%, meeting the primary endpoint. Patients reported significant improvements in pain severity, interference scores, quality of life, and insomnia. There was one grade 3 adverse event (dizziness) related to the study drug. A significant decrease was noted in serum C-terminal telopeptide levels with therapy. CONCLUSION: Our pilot study shows that the addition of dronabinol resulted in decreased opioid requirements for CIBP. Patient-reported outcomes also demonstrated improved pain and QOL with addition of dronabinol. Our results are promising and warrant further investigation into novel analgesics for CIBP to decrease opioid use.