NEW YORK – Scientists are reporting the first clear success with a new approach for treating leukemia, turning the patients’ own blood cells into assassins that hunt and destroy their cancer cells.

It has only been done in three patients so far, but the results were striking: Two appear cancer-free up to a year after treatment, and the third patient is improved but still has some cancer. Scientists are already preparing to try the same gene therapy technique for other kinds of cancer.

“It worked great. We were surprised it worked as well as it did,” said Dr. Carl June, a gene therapy expert at the University of Pennsylvania. “We’re just a year out now. We need to find out how long these remissions last.”

He led the study, published Wednesday by the New England Journal of Medicine and Science Translational Medicine.

It involved three men with very advanced cases of chronic lymphocytic leukemia, or CLL. The only hope for a cure now is bone marrow or stem cell transplants, which don’t always work and carry a high risk of death.