Good morning. His oncologist may be able to request a consult with a dietitian. That may be helpful in managing some treatment side effects, especially any GI issues.
The biopsy results should drive the treatment plan, there are many types of lung cancer with a variety of treatments and side effects.
Personally, I believe that the treatment (targeted therapy) is keeping me alive, and the cancer will come back no matter what I eat. I do make sure I drink lots of water and I try to eat enough fiber to keep my digestive system happy, because the meds that I take can be rough on that area.
Taking charge of what you eat can be a way to feel like you have some control, during a time when our bodies have betrayed us, and we feel that we have very little control of the situation and our futures. While many feel that they are going to die either way, so they eat and drink what they want; enjoy life and food!
There’s no one right answer, but some input from a registered dietitian may be a good place to start, they are trained to deal with the diet and the psychological relationship that we have with food too. Good luck to you and him! Take care, Lisa