Besides spreading cancer cells, chemo inflicts serious and perhaps irreversible damage to the immune system, the body's natural first line of defense against cancer and other illness - thus paving the way for the remaining cancer cells or future cancers to overwhelm a body that is even less able to beat the cancer that got past the immune system in the first place.
Taken from the 100% plant based diet book "The RAVE diet"
"Another reason why animal protein causes Cancer has to do with digestive enzymes - or a shortage of them as a result of eating animal foods. Cancer cells have a protective protein coating around them which makes them invisible to the immune system. The pancreas produces two enzymes that help digest animal protein. In addition to digesting animal protein, only these enzymes can dissolve the protein coating around the cancer cells. Once the protein coating is disolved by the enzymes, the cancer cells become visible and the immune system can do it's job of destroying them.
Animal protein requires a lot of enzymes to digest it and eating a diet high in animal protein can cause a shortage of pancreatic enzymes. When this happens, cancer cells will keep their protective protein coating and remain invisible to the immune system - and start multiplying. The more animal protein you eat, in other words, the more you impair your body's natural defenses against cancer."
He references the following:
This was first documented by Dr. John Beard in his book published in 1911, The enzyme treatment of cancer and it's scientific basis. For more information, see the write up in Richard Walters, Options - The Alternative Cancer Therapy Book.
The two enzymes produced by the pancreas are "Tripsin and chymotripsin"