Brief Title Mechanisms of Cancer-Related Pain and Opioid Use Among Adolescents and Young Adult Sarcoma Survivors: Pilot Feasibility Study

This study is trying to understand why some young cancer survivors experience chronic pain after being treated for sarcoma (bone or soft tissue cancer), and how opioid pain medications affect them. It is a pilot study focused on teens and young adults. **You may be eligible if...** - You were diagnosed with sarcoma between ages 12 and 24 - You are currently under 70 years old and enrolled in survivorship care - Your cancer is currently showing no signs of active disease - You have meaningful ongoing pain (rated 3 or higher on a 0–10 scale) related to your cancer or treatment - You have a smartphone with internet access **You may NOT be eligible if...** - You are currently receiving active cancer treatment - You are unable to read or speak English fluently - You cannot complete assessments on your phone over a 3-month period Talk to your doctor to see if this trial is right for you.