 - To determine whether methadone used as first line strong opioid is superior to morphine as evidenced by reduced pain over a 12-week treatment period in patients with advanced cancer. Previous studies have demonstrated consistent improvement of pain control after opioid rotation from morphine to methadone. In addition, the pilot study showed that there was a trend towards lower pain intensity when methadone used as first line opioid as compared to morphine. Researchers postulate that due to its superior analgesic effects, methadone will result in better pain control over time as compared to morphine. 