Absolute Lymphocyte Count Recovery Independently Predicts Outcome in Childhood Acute Lymphoblastic Leukemia: Experience From a Tertiary Care Cancer Center of a Developing Country

Background: Accurate risk stratification is essential for successful treatment outcome in childhood acute lymphoblastic leukemia. Early recovery of absolute lymphocyte count (ALC) during induction therapy is emerging as a reliable favorable prognostic indicator that may hold its relevance in resource-constraint settings.

Materials And Methods: This is a retrospective chart review of medical records of 212 patients of acute lymphoblastic leukemia, aged less than 18 years, treated between January 1996 and December 2009. Time to lymphocyte recovery was analyzed with respect to various prognostic factors and survival and Martingale residuals were used to define ALC cut-offs.

Results: High-risk disease characteristics including older age (10 y and older), National Cancer Institute high risk, and central nervous system disease at diagnosis were associated with delayed lymphocyte recovery. The 5-year event-free, relapse-free, and overall survival of patients with day 15 ALC of ≥ 500 cells/µL and day 29 ALC of ≥ 1000 cells/µL was 81.7% ± 4%, 86.4% ± 2.8%, 91.0% ± 3%, respectively, compared with those with delayed recovery (16.6% ± 5.6%, 19.3% ± 6.4%, 32.8% ± 7.2%, P < 0.001). In multivariate analysis both these ALC cut-offs retained their significance as prognostic variables of survival.

Conclusion: Our analysis revealed ALC to be an important independent predictor of treatment outcome and may provide key prognostic information in settings where minimal residual disease-based risk stratification is not feasible.