Residual leukemia cannot be detected in very early remission peripheral blood stem cell collections in acute non-lymphoblastic leukemia.

We have used a combined cell culture and cytogenetic approach to study the level of residual leukemia during the very early remission (VER) phase of acute non-lymphoblastic leukemia. Clonogenic leukemic cells were induced to proliferate by phytohemagglutinin-stimulated leucocyte conditioned medium and identified by a leukemia-associated karyotype t(8;21) and a morphological marker (Auer rod). When leukemic blasts were cultured, the leukemic karyotype and Auer rods were most readily detected after 3-9 days. When VER blood cells were cultured, no leukemia-associated karyotype or Auer rods could be detected. Based on the number of VER blood cell derived metaphases analysed, the incidence of leukemic blasts among dividing cells is less than 2%.