I fully understand the feeding tube. I've had mine for 3 years. Protein powder is a big calorie booster as well as a Tbs of olive oil. I'm sure you probably on formula but these can easily be added to that. You can maintain a reasonable weight but you'll have to boost calories where you can.
Bryan

15 year survivor of tonsil cancer. In 2002 I was diagnosed with Stage III squamous cell carcinoma. I had a left neck dissection, teeth removed, and 38 radiation treatments. In 2015 I received a feeding tube and in 2016 a trach, both due to radiation side effects. But I'm happy to say that life has been good to me!!