I have taken several rounds of DEC, usually ramping up to 600mg/ day divided into 3 doses but recently took some lower dose for a week. In a Lyme book I have, the author claims it did not help him at first try but later made a big improvement for him. I wish I could find the article he referenced. I had It bookmarked but can't find it. Anyway it seems DEC does allow the immune system to "see" invaders which were previously not seen and that it actually improves liver function or at least is hepatoprotective.
This is what I feel it did for me though since I still don't have a definitive diagnosis I can't be sure of anything. Worth a shot, especially if you have been pounding away at your liver.