Study of promising cancer treatment allowed to resume

A study of an experimental treatment for leukemia that was halted last week following two patient deaths has been allowed to resume after a modification.

The Food and Drug Administration suspended Juno Therapeutics' trial after the company reported that two patients died from swelling of the brain. Juno said the problem stemmed not from its treatment, but from a chemotherapy drug used as a pre-treatment step. The FDA will allow the trial to resume without that chemotherapy drug.

Juno's treatment is a promising, but still unproven, approach that reengineers patients' immune systems to attack cancer. White blood cells are removed from the patient and altered so they can target cancer cells when returned to the body.

Juno shares were up 27 percent in trading after the market closed Tuesday.