ALL-245: Association of Absolute Lymphocyte Count (ALC) with Event-Free Survival (EFS) and Overall Survival (OS) in Pediatric B-Cell Acute Lymphoblastic Leukemia (B-ALL)

Context: Absolute lymphocyte count has been evaluated as a prognostic factor in pediatric B-ALL. However, few prospective studies are available with BFM-90 protocols in a uniform group of patients, and there is a lack of consensus regarding the optimum cutoff for ALC as a prognostic factor. Objective: This study was done to evaluate the association of ALC with EFS and OS in pediatric B-ALL. Outcomes: Association of ALC at baseline, day 8, day 15, and the end of induction with EFS and OS was evaluated in pediatric B- ALL. Designs: It was a prospective study conducted from July 2015–June 2017. Setting: The study was done in a tertiary cancer institute in India. Patients: De novo B-ALL patients between age 1 and 18 years were included. 20 May 2021 was the cutoff date for EFS and OS data analysis. Total leukocyte count was done on MS95s (MeletSchloesing Laboratories, Osny, France) at baseline, day 8, day 15, and the end of induction. Simultaneously, a peripheral smear was made, and a manual differential count was done to determine the percentage of lymphocytes. ALC was calculated as a percentage of lymphocytes multiplied by total leukocyte count. ALC was categorized into two categories taking cutoffs at 0.5×109 cells/l, 0.75×109 cells/l, 1×109 cells/l, and 1.5×109 cells/l. EFS and OS for these categories were evaluated by Kaplan–Meier method. Results: For the two-year duration, 197 B-ALL patients were recruited, of which 150 were analyzed. We found that day 8 ALC >1.5×109 cells/l was associated with poor OS (HR: 2, CI: 1.24–3.24, P=0.004), whereas ALC >1.5×109 cells/l at the end of induction was associated with significantly better OS (HR: 0.51, CI: 0.30–0.86, P=0.01) and better EFS (HR:0.49, CI: 0.30–0.80, P=0.004). ALC cutoffs at baseline and day 15 were not associated with EFS and OS. Conclusions: In our prospective study, we found that ALC >1.5×109 cells/l predicted better EFS and OS in pediatric B-ALL. A larger sample size is needed to establish ALC as a predictor of EFS and OS.