Early chemosensitivity of normal hematopoietic cells and malignant lymphoblasts predicts relapse in childhood acute lymphoblastic leukemia

For the last 30 years, numerous clinical and biological pretreatment risk factors have been utilized for risk-based treatment assignment in childhood acute lymphoblastic leukemia (ALL). However, with improved chemotherapy regimens, many of these traditional prognostic factors have lost clinical significance. We aimed to improve relapse prediction in children with ALL through evaluation of the early chemosensitivity of normal and malignant cells and to determine the relationship between such chemosensitivity and risk of relapse. We retrospectively analyzed a cohort of 60 children with newly diagnosed ALL of whom 40 patients were in complete remission for at least 4 years and 20 patients relapsed during or following treatment. Time to peripheral blood blast clearance (PBBC) was used as a measure of chemosensitivity of malignant lymphoblasts while end-of-induction complete blood count (CBC) parameters were used as a measure of chemosensitivity of normal hematopoietic cells. Our results showed that longer time to PBBC and lower end-of-induction total leukocyte count (TLC) and absolute neutrophil count (ANC) were significantly associated with increased risk of relapse. In conclusion, time to PBBC and end-of-induction TLC and ANC are important predictors of relapse and should be used to modify the intensity of chemotherapy at earlier time points during the course of treatment. A wider prospective, randomized, controlled trial is required to confirm our results.