Enzyme therapy was first proposed by John Beard, a doctor who worked with this type of therapy in 1906. He noted that, when giving pancreatic enzymes (digestive enzymes), the body was able to defend itself better from cancer. He proposed that enzyme therapy could be used in any type of cancer.
One article (1) discussed enzyme therapy and the treatment of cancer. It noted that enzyme therapy stopped being used in medical circles after Dr. Beard’s death. It has since been rediscovered as a possible treatment for cancer. Because the enzymes are destroyed by the stomach, they need to be injected before being used as a cancer treatment.
Some doctors are still using pancreatic enzymes orally for the treatment of cancer, citing that the enzymes are stable in stomach acid and can pass through, being absorbed by the small intestines.
Source: 1.Enzyme Therapy and Cancer. http://www.dr-gonzalez.com/history_of_treatment.htm. Accessed 9/7/16.