“This study compared the efficacy of a tetrahydrocannabinol:cannabidiol (THC:CBD) extract, a nonopioid analgesic endocannabinoid system modulator, and a THC extract, with placebo, in relieving pain in patients with advanced cancer. This study shows that THC:CBD extract is efficacious for relief of pain in patients with advanced cancer pain not fully relieved by strong opioids.”  http://www.ncbi.nlm.nih.gov/pubmed/19896326

“In conclusion, THC:CBD extract, a nonopioid analgesic, endocannabinoid system modulator, has been shown to be a useful adjunctive treatment for relief of pain in patients with advanced cancer who experience inadequate analgesia despite chronic opioid therapy. The reductions in pain scores were neither because of a change in opioid background medications nor because of an increase in use of breakthrough medication. Therefore, we can conclude that the observed reduction in pain scores is attributable to the positive analgesic effects of THC:CBD extract.” http://www.jpsmjournal.com/article/S0885-3924(09)00787-8/fulltext