A cancer therapy involving a patient's own immune cells is showing extraordinary results in leukemia patients, researchers say.

In the latest study, U.S. researchers used genetically modified T-cells in 35 terminally ill patients with leukemia, and 94 percent went into remission.

"A type of blood cell in the body called a T-cell was reengineered and tricked into fighting the cancer," Perlmutter Cancer Center's Dr. Michael Grossbard, a specialist in leukemia, lymphoma and oncology, told CBS News.

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The technique involves removing T-cells from the patient's body. The cells are modified with molecules from genetically engineered mice, known as chimeric antigen receptors, or CARS. The cells are then infused back into the body. The CARS molecules reduce the ability of the cancer to shield itself from the patient's natural immune system, allowing the T-cells to attack the cancer.

A similar technique was recently used in the U.K. for the first time to save the life of one-year-old leukemia patient Layla Richards. It's the first time doctors there are seeing larger numbers of patients coming through and being as successfully treated as the small numbers of patients that first underwent the experimental treatment.

Another trial in Italy saw modified T-cells remain in the body for 14 years. The hope is that by using this technique, cancer could eventually be kept at bay over a lifetime.

The T-cell treatment works best with blood cancers rather than tumors. Patients can experience difficult side effects, but experts are excited about the results.

"Oncologists are reluctant to use the word extraordinary, but these are extraordinary. These are really remarkable findings that have a significant response for patients," Grossbard said.

The studies were conducted in patients with acute lymphoblastic leukemia and non-Hodgkin's lymphoma. Patients who had previously failed conventional therapies, including stem cell treatments and chemotherapy, had "very significant responses to these treatments," said Grossbard.

Eventually, doctors hope the treatment option will be available for more patients, including those with other types of cancer.

"The hope is that as we go forward, this will be available in more types of leukemia and lymphoma, and even what we call solid tumors," Grossbard said. "I would expect that there should be some major advances applicable to a broader number of patients within the next three to five years."

Also on the immuno-oncology front, Reuters reported today that the U.S. Food and Drug Administration has granted "breakthrough therapy" designation to AstraZeneca's durvalumab drug as a treatment for bladder cancer. Breakthrough therapy designation speeds up the development and review of medicines aimed at treating serious and life-threatening diseases.