This prospective study will recruit patients with pain related to cancer or its treatment who are on buprenorphine in combination with a full agonist opioid where dose of the full agonist opioids (FAO) is > 30 mg OME per day. They will be provided a mobile application (CPM Rx) for reporting of pain level daily and at each as needed dose. Withdrawal will be assessed using a modified Clinical Opioid Withdrawal Scale (COWS) score and patients will be instructed to be aware of changes in these symptoms. They will also be followed in person at the initial visit, and at days 14, 28, 56 , and 84 with Brief Pain Inventory (BPI) and COWS scale to assess for pain or withdrawal and other reported side effects. Pill counts will be done on days 28, 56, and 84 to further assess medication usage. Nurses will check-in to complete BPI and ask about withdrawal symptoms at days 42 and 70. The study seeks to assess if patients on buprenorphine and FAO have withdrawal symptoms, what are the highest doses of buprenorphine and FAO tolerated, and assess usage of the CPM Rx app. Each patient will be followed on the study for 3 months, unless the choose or it is deemed appropriate to end sooner.