Can keep food down after Radiation/Chemo

Hello, my mom was diagnosed with stage 3.5 stomach cancer. They removed 3/4 of her stomach right away. They then started on chemo and radiation for the infected areas. Soon after treatment she was told the cancer was in remission. Since that time she can't keep any food down. It has been about two months and she has lost about 40 pounds. The doctors have tried feeding tubes and numerous anti-nausea meds. But all to no avail. Every doctor she has seen seems to have no idea what is wrong. She has barely ate in 2 months. Everything makes her vomit the contents back up. Every diet we have tried has failed. I am very worried and have no idea what to do. Any suggestions would be appreciated. Thanks.