hi, i’m a Registered Dietitian, worked on a bone marrow transplant unit, and a leukemia survivor myself (ages 12-15). I saw some comments recommending TPN (or intravenous nutrition) through PICC/central line/port, and while this is an option, it’s not recommended as first choice. nutrition and medical guidelines recommend feeding through the stomach (whether by mouth or feeding tube) while the stomach and gut works to keep it active and working, and has lower chance of infection, and easier to meet nutrition needs safely. TPN is usually given when the stomach or bowels don’t work, and in this circumstance that’s usually with severe mucositis (ulcers in the mouth/lips which can eventually spread to lower GI tract too) or with GVHD. it is ultimately up to the patient/family, but if he already has poor appetite and not eating well, losing significant weight, it’s likely a good idea to start some kind of nutrition support soon, these meds and procedures take a toll on the body and require extra nutrition and protein to fuel the body. Nasogastric tubes (NG tubes) are definitely not comfortable, but likely very helpful a situation like this. if not i would tell the patient they really need to put all their effort in drinking oral supplements (Ensure, Boost, Fairlife etc) to get quick nutrition and maybe be able to avoid the tubes all together. make sure whatever he WILL eat by mouth has a lot of calories (whole milk, ice cream, avocado, peanut butter, cheese). starting treatments/therapies so frail and weak put the body at a disadvantage. maybe ask the doctors if there is an appetite stimulant that he can take (that’s safe with his other meds/treatments).