Nine leukemia patients are cancer-free after being treated with genetically altered versions of their own immune cells, giving strength to a promising new approach for treating the blood cancer.

The trial of 12 patients, two of them children, bolsters findings from 2011. Then, scientists from the University of Pennsylvania reported that two of the first three patients treated showed no traces of the malignancy after the therapy. The results were presented Sunday at the annual meeting in Atlanta of the American Society of Hematology.

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For Walter Keller, 59, for whom every other treatment for chronic lymphocytic leukemia diagnosed in 1996 had failed, the regimen meant he's been in remission since treatment in April. Before the therapy, "I thought I had a year to live," he said. "I feel better than I have in a long, long time," said Keller, of Upland, Calif. "I'm excited because I think this will help a lot of people."

The approach has since been acquired by Novartis AG. -- Bloomberg News