My father has lung cancer and has been on chemo but doesn't change much. Now he is really skinny due to his appetite. Could u advice what other safe treatment?

Stage 3-4. Chemotherapy +/- radiation, is the main therapy for stage iii, IV lung cancers and small cell(oat cell) carcinomas. However staging indicates that the disease process is systemic. Therefore, in advanced stage lung cancers, the patients are usually weak from malnutrition with low pre albumins, and maybe also post obstructive pneumonia. Try to help his nutrition withpulmocarechilleddrinks.Oncologist.
Check Sanoviv. There are some medications that can help with appetite. Otherwise, check on gerson therapy and sanoviv.
It is a challenge.. Despite continuing advancement in cancer treatments, it is very difficult/challenging for advanced cancer. Treatments are often toxic and cause much side effects, including appetite loss. I'm sure his oncologist is working on alternative regimen. Consult doc for appetite-enhancing meds to help with food intake/improve nutrition as this is very important. Wish him the best of luck for me...
Hard to say. Would need to know a lot more about his situation. There are some appetite stimulants. If he is not on one, it might be something to consider.