This study will enroll patients scheduled to receive radiation therapy (RT), but RT details are not specified by this protocol. Patients taking long acting opioid analgesics prior to enrollment will be converted to an equivalent dose of Xtampza ER at the time of enrollment. For the remaining patients not previously prescribed opioid analgesics, Xtampza ER will be initiated when 2 or more daily doses of short acting opioids are required, resulting in a total daily dose of at least 30mg morphine sulfate equivalent. During RT, pain will be assessed on a weekly basis using the PI-NRS and the dose of Xtampza ER will be adjusted at the discretion of the treating physician, with recommendation to maintain an equivalent of 100% daily opioid requirement. Assessment for tapering of Xtampza ER will begin 1 month following the completion of RT at the time of first follow-up.The study period will end 3 months following the final fraction of RT.

Xtampza ER is a wax microsphere formulation of oxycodone that results in a nearly identical pharmacokinetic profile regardless of whether the capsule is intact when ingested or if ingested via enteral feeding tube as opposed to by mouth.

Feasibility of administering Xtampza ER during RT is defined as continuation of the medication throughout RT. The number of patients who discontinue Xtampza ER due to difficulty with administration, perceived inefficacy, or toxicity will be recorded.

Pain will be assessed using:

Pain Intensity Numeric Rating Scale - a scale of 0-10, with 0 being no pain and 10 being worst possible pain.

Brief Pain Inventory - a patient completed 2-page questionnaire rating severity of pain and how pain interferes with functioning. The pain severity score is calculated by averaging the 4 questions related to this topic (each question is a 0-10 scale, with higher numbers indicating worse pain). The pain interference score is calculated by averaging the 7 questions related to this topic (each question is a 0-10 scale, with higher numbers indicating worse functional interference). The remaining items included in the Brief Pain Inventory will be recorded but do not contribute to a score.