Through her work with cancer patients, Caisse observed that Essiac broke down nodular masses to a more normal tissue, while greatly alleviating pain. Many patients would report an enlarging and hardening of the tumor after a few treatments. Then the tumor would start to soften. People also frequently reported a discharge of large amounts of pus and fleshy material. Masses of diseased tissue were sloughed off in persons with breast, rectum, and internal cancers. After this process, the tumor would be gone.3

Caisse theorized that one of the herbs in Essiac reduced tumor growth while other herbs acted as blood purifiers, carrying away destroyed tissue as well as infections related to the malignancy. She also speculated that Essiac strengthened the body's innate defense mechanisms, enabling normal cells to destroy abnormal ones as Nature intended.

Even if a tumor didn't disappear, Caisse maintained, it could be forced to regress, then surgically removed after six to eight Essiac treatments, with much less risk of metastasizing and causing new outbreaks. "If there is any suspicion that any malignant cells are left after the operation," she stated, "then Essiac should be given once a week for at least three months, supplying the body with the resistance to a recurrence that is needed."

She wrote, "In the case of cancer of the breast, the primary growth will usually invade the mammary gland of the opposite breast or the auxilla, or both. If Essiac is administered either orally or by hypodermic injection, into the forearm, the secondary growth will regress into the primary mass, enlarging it for a time, but when it is all localized it will loosen and soften and can then be removed without the danger of recurrence."4 Caisse spoke from personal experience, having administered thousands of Essiac injections to gravely ill patients, always under the supervision of a physician.

In 1983, Dr. E. Bruce Hendrick, chief of neurosurgery at the University of Toronto's Hospital for Sick Children, urged Canada's highest health officials to launch "a scientific clinical trial" of Essiac. In a letter to the Canadian Minister of Health and Welfare, Dr. Hendrick reported that eight of ten patients with surgically treated tumors of the central nervous system, after following an Essiac regimen, had "escaped from the conventional methods of therapy including both radiation and chemotherapy."5 Yet today, patients in Canada must go through a bureaucratic maze that makes it difficult or impossible for them to receive Essiac therapy.

The story of Essiac began in 1922, when Caisse, a surgical nurse working in a Haileybury, Ontario, hospital, noticed an elderly patient with a strangely scarred, gnarled breast. When Rene asked the woman, who was nearly eighty, what had happened, the woman replied that some thirty years earlier, she had developed a growth on her breast and an Indian friend had offered to heal it with herbal medicine. This woman and her husband then went to Ontario, where doctors confirmed the diagnosis of advanced cancer and told her the breast would have to be surgically removed. Opting instead to take her chances with the Indian herbal healer, the woman returned to his mining camp and drank the brew daily. Her tumors gradually shrank, then disappeared. Over two decades later, when Caisse stumbled across her in the hospital, she was still totally cancer-free.

Caisse asked the woman for the herbal recipe. "My thought was that if I should ever develop cancer, I would use it," Caisse later wrote.