Methadone for 'Adenocarcinopathic' Pain Treatment

Methadone is an opioid that has been used for over 80 years to treat various types of pain, including cancer pain. Despite its increasing popularity as a co-analgesic and first-line treatment for cancer pain, there remain some outstanding questions regarding its use in treating cancer pain, such as its efficacy compared to other opioids and its appropriateness as a first-line treatment. The investigators will conduct a Vanguard Randomized Clinical Trial (RCT) to estimate the efficacy of methadone compared to morphine for the treatment of a newly defined type of cancer pain, which the investigators have termed 'adenocarcinopathic' pain (ACPP).