The Gerson Therapy diet, as I understand it, is orgainic raw vegan with lots of fresh whole-fruit juices, plus IV drip vitamin C, and it seems to work (from what I've read).
Completely eliminating processed junk is definitely a step in the right direction for ANY cancer patient.
Part of the reason that meat is "unhealthy" is that the "meat" being referred to is CAFO and/or processed meats, which have a lot of non-optimal things in them which essentially FEED the cancer cells.
My personal feeling is - if I were diagnosed with cancer, I would definitely pay even closer attention to my diet, eliminating as much of the "20%" as possible, especially sugars. If I couldn't afford pastured meat, I might go meatless in an effort to starve the cancer. Good quality meat makes me feel ALIVE, so I would probably just eat as much pastured beef as I could afford. (Veggies also make me feel awesome, so no problem there)