In December, we told you how doctors at Children's Hospital trained Emma Whitehead's own disease-fighting T-cells to attack her acute leukemia.
Now, doctors at Memorial Sloan-Kettering Hospital have used it for acute adult leukemia.
It didn't work for everyone in the small experiment, but it did for ABC sound technician David Aponte.
In 8 days, all traces of his leukemia were gone.
Aponte has since had a bone marrow transplant, and is doing well.
ABC medical editor Dr. Richard Besser sees a lot of promise in the new therapy.
"You could target them to go after all different types of cancers. So, the theory is, maybe you would target them to go after prostate cancer or breast cancer. It's an endless approach," Besser said.
One drawback is that it takes a month to engineer white blood cells to become cancer-fighting cells, but acute adult leukemia can be deadly in weeks.
Tests with the treatment are continuing here and elsewhere around the country.