This story has understandably been attracting wide attention given the novel use of immunotherapy: using a disabled form of the AIDS to reprogram the immune system genetically to kill cancer cells (using T-cells).
The poster child (a bouncing 6-year old named Emma) for the experimental treatment is doing well, although not all patients have had the same success. While of great promise for a variety of blood cancers, still in early stages as per the quote below:
The research is still in its early stages, and many questions remain. The researchers are not entirely sure why the treatment works, or why it sometimes fails. One patient had a remission after being treated only twice, and even then the reaction was so delayed that it took the researchers by surprise. For the patients who had no response whatsoever, the team suspects a flawed batch of T-cells. The child who had a temporary remission apparently relapsed because not all of her leukemic cells had the marker that was targeted by the altered T-cells.