out of options, he was being treated for leukemia, a rare and often fatal disease in adults. when chemotherapy failed, doctors turned to an experimental treatment. robin roberts went to visit him in december. i think i am on the right road. i think i am on the right road. reporter: doctors took out millions of david s disease fighting white blood cells. then used a retro virus which is great to getting into human immune systems to turn the cells into targeted cancer fighters. david s cells went back in and destroyed the cancer. acting like a living drug. the first patient to have similar treatment was 7-year-old emma whitehead. she is in complete remission. she has a ton of energy. she is doing wonderful right now. reporter: researchers report on the safety of the treatment in five more patients. what we saw just blew us away. the cancers went away in a matter of weeks, even days. reporter: days? days in one case.
54%. now, you might be wondering, there are other things you can do that can reduce your risk of infection by a lot more. i m going to talk to you about this. theish sue using this consistently. remember, this is going to be used by women who are doing what they can do to reduce the spread of infection. not men who could choose to wear condoms. in this case, the gel has to be applied up to 12 hours before sexual intercourse, and within 12 hours after it. so there are some requirements here. and that is part of the challenge of applying it consistently. now, the gel contains something called an anti retro viral microbeside. we ll talk to someone about this. hiv is a retro virus, so it s an anti retro viral microbeside. up until now we weren t sure these would work, particularly in women. but it stops the hiv virus from attacking the system. it is the first completed study on one of these things, and the