Complete Peripheral Blast Clearance is Superior to the Conventional Cut-Off of 1000/µL in Predicting Relapse in Pediatric Pre-B Acute Lymphoblastic Leukemia.

Abstract

Risk-stratification has contributed to a dramatic improvement in survival in pediatric acute lymphoblastic leukemia (ALL). This study evaluated the utility of prephase response and day 15 bone marrow when a minimal residual disease (MRD) assessment was available. A file review of children aged ≤ 15years diagnosed with precursor-B ALL from 2014 to 2019 was performed. The protocol used for risk stratification and treatment was based on a UKALL-2003 backbone. All patients received one week of prephase therapy comprised of intravenous dexamethasone in the first 48h followed by oral prednisolone. The median age of the 255 patients in the study was 5years. Following the prephase, the peripheral blood absolute blast count was 0 and ≥ 1000/µL blasts in 141 (56%) and 29 (11%), respectively. Ten of 199 (5%) patients with an evaluable day 15 bone marrow had M3 status. At the end of induction, 30 (12%), 127 (50%) and 98 (38%) patients belonged to the standard-risk, intermediate-risk and high-risk (HR) groups, respectively. An M3 day15 bone marrow was the sole reason for escalation in three (3%) of the patients in the HR group. A lack of complete clearance of peripheral blood blasts post-prephase [HR: 2.45 (1.04-5.75), p = 0.040] and a positive MRD [HR: 3.00 (1.28-7.02), p = 0.011] independently predicted risk of relapse. Complete blast clearance is superior to the traditional cut-off of 1000/µL in predicting relapse. The role of a day 15 bone marrow morphology is diminished when an end of induction MRD is available.