I haven't followed the Gerson Therapy but I can tell you two stories:
-One of my co-workers just finished the juice fast recommended in the documentary, "Fat, Sick, and Nearly Dead" and said she feels better than she has in a long time. She also said a friend of hers, 32 years old with cancer throughout his body, is on the juice fast and is responding remarkably well.
-I was diagnosed with breast cancer in 2006, the tumor was 2 centimeters, estrogen receptive, and cancer was found in one lymph node. My medical team recommended chemo and radiation as a preventative measure. I remembered that thirty +/- years ago, my dad had told me of a clinic in Germany he'd read about that had success curing terminal cancer patients by eliminating refined white flour and sugar, caffiene, alcohol, and salt from the patients' diets. Immediately following diagnosis, I completely eliminated every food containing artificial ingredients, any processed or packaged foods, all dairy, all sweeteners, all alcoholic beverages, all fried foods, and avoided anything made with safflower or canola oils. Basically, I ate lots of vegetables (mostly organic), limited fruit (organic), some lean protein (organic, grass fed/grass finished), and drank filtered water.
I am allergic to dairy and most sugars (including honey and fructose), but until diagnosis, I had eaten it anyway and suffered the consequences. I hadn't known I was also allergic to gluten until after chemotherapy, which eliminated everything made of wheat, barley, spelt, rye, etc.
I refused to take Tamoxifen or any of the other inhibitor drugs once I finished with chemo because there were too many side effects. I chose, instead, to maintain the strict diet. I am now a 6-year survivor and feel better than I ever did prior to diagnosis. This way of eating also had some side benefits: (1) chemo threw me into early menopause, but by avoiding sweetened foods, alcohol, and simple carbohydrates, hot flashes were mild and quick; (2) no more insomnia!!!; (3) my energy lasts all day--no more "afternoon slump"; (4) I stay trim without having to watch my weight.
I am somewhat skeptical about some of the components of the Gerson Therapy, but if I knew in 2006 what I know now, I probably would have tried the Gerson Therapy.