I would ask your oncologist if Mayo provides physical therapy for cancer patients. When we are in pain we tend to scrunch forward and become tight in the front delta and pectoral muscles. Exercises that strengthen and stretch these frontal areas releases tension on the upper back. There are also very specific stretches that work these upper back muscles. Google search "Physical Therapy Upper Back Pain" and look for credible sources for instructions and videos. If you can't get to a physical therapist on your insurance, you should be able to find some helpful resources online. Lastly, if the area seems inflamed, try icing 20 minutes on, 20 minutes off. If no inflammation, heat treatment will help relax the muscles and promote healing. Feel free to reach out with questions.