In 1947, the NCI reviewed ten cases selected by Dr. Gerson and found his report unconvincing. That same year, a committee appointed by the New York County Medical Society reviewed records of 86 patients, examined ten patients, and found no evidence that the Gerson method had value in treating cancer. An NCI analysis of Dr. Gerson?s book A Cancer Therapy: Results of Fifty Cases concluded in 1959 that most of the cases failed to meet the criteria (such as histologic verification of cancer) for proper evaluation of a cancer case . A recent review of the Gerson treatment rationale concluded: (a) the ?poisons? Gerson claimed to be present in processed foods have never been identified, (b) frequent coffee enemas have never been shown to mobilize and remove poisons from the liver and intestines of cancer patients, (c) there is no evidence that any such poisons are related to the onset of cancer, (d) there is no evidence that a ?healing? inflammatory reaction exists that can seek out and kill cancer cells .And:
Charlotte Gerson claims that treatment at the clinic has produced high cure rates for many cancers. In 1986, however, investigators learned that patients were not monitored after they left the facility . Although clinic personnel later said they would follow their patients systematically, there is no published evidence that they have done so. A naturopath who visited the Gerson Clinic in 1983 was able to track 21 patients over a 5-year period (or until death) through annual letters or phone calls. At the 5-year mark, only one was still alive (but not cancer-free); the rest had succumbed to their cancer 
this is cancer quackery.... plain and simple.
The (Not-So-)Beautiful (Un)Truth about the Gerson protocol and cancer quackery ? Science-Based Medicine