A new way of genetically altering a patient’s cells to fight cancer has helped desperately ill people with leukemia when every other treatment had failed, researchers reported on Monday in the journal Nature Medicine.

The new approach, still experimental, could eventually be given by itself or, more likely, be used in combination treatments — analogous to antiviral “cocktails” for H.I.V. or multidrug regimens of chemotherapy for cancer — to increase the odds of shutting down the disease.

Researchers say the treatment may be more promising as part of a combination than when given alone because, although some patients in the small study have had long-lasting remissions, many others had relapses.

The research, conducted at the National Cancer Institute, is the latest advance in the fast-growing field of immunotherapy, which fires up the immune system to attack cancer. The new findings build on two similar treatments that were approved by the Food and Drug Administration this year: Kymriah, made by Novartis for leukemia; and Yescarta, by Kite Pharma for lymphoma.