Time course of peripheral blood count recovery during induction chemotherapy for childhood acute lymphoblastic leukemia.

Introduction: Children with newly diagnosed acute lymphoblastic leukemia (ALL) present with low peripheral blood counts caused by bone marrow replacement. The recovery of counts during induction chemotherapy is not well described. Material and methods: Records for 63 children with ALL were reviewed. Peripheral hematology blood counts during five weeks of induction chemotherapy were extracted, and the time to partial recovery with safe counts and complete recovery with normal counts in the three cell lines determined. The number of red cell and platelet transfusions, the number of febrile episodes, and the number of days on intravenous antibiotics were counted. Results: Platelet recovery occurred early: median time to achieving counts >50/nL 14 days, to counts >100/nL 16 days. Neutrophil recovery was relatively slow: median time to counts >0.5/nL 18 days, to counts >1.0/nL 26 days. The time to partial recovery was shorter in high risk than in lower-risk treatment groups. Partial platelet recovery by day 15 indicated early recovery and lower morbidity. Complete platelet recovery day 15 was significantly associated with residual disease <0.1% after four weeks. Lymphocyte counts showed a marked decrease in first two weeks followed by a rise in the next three weeks; a count <0.35/nL on day 15 was associated with poor response. Conclusion: After starting chemotherapy for ALL, platelet recovery can be expected after two to three weeks while neutrophil recovery lasts three to five weeks. Platelet and lymphocyte counts after two weeks treatment may give an indication of residual disease after four weeks.