Marianne,
Alcohol will dry out the mucousa (sp) and cause damage on a cellular level that can lead to cancer. The threat of that through the feeding tube is negated and you only have to worry about your liver at that point depending on how heavy you are on the sauce.

Having a drink through your tube is actually a safe way to go, many of us have. Charm, who cannot take food or water orally relies soley on his PEG and regularly enjoys wine with his wife. Myself, I used to shoot whiskey through mine when I needed a drink (not recommended as you get drunk very quickly as there is no burn) and enjoyed the desired effects. Not safe if you are on opiate pain meds though as it'll slow your already hampered cardiovascular system.
Bottoms up
Eric