Catherine Wu, MD, Dana-Farber Cancer Institute, Boston, MA, discusses the differences in leukemic cells that relapse after stem cell transplant therapy. Patients with leukemic cells that have relative clonal stability before and after transplantation relapse very early. Suggesting that the pressure from immunotherapy is not sufficient. Leukemic cells with some clonal evolution cause a delayed relapse. In these cases, a large proportion of the cells were eliminated, however, some clones survived. This interview took place during the European Research Initiative on CLL (ERIC) International Virtual Meeting 2020.