Patterns of relapse and survival outcomes in pediatric ALL from a single center cohort under the CCCG ALL 2015...

To characterize relapse patterns, identify relapse-related risk factors, and evaluate prognostic determinants of post-relapse outcomes in pediatric acute lymphoblastic leukemia (ALL) patients treated with the Chinese Children's Cancer Group (CCCG)-ALL-2015 protocol.

This retrospective study included 380 children diagnosed with ALL between 2016 and 2019. We analyzed relapse timing (very early, early, late), relapse sites (bone marrow (BM) vs. extramedullary), early treatment response (morphology and minimal residual disease (MRD)), and post-relapse outcomes. Survival was estimated using Kaplan-Meier methods.

Relapse rate was 11.1% (42/380), predominantly isolated BM (69.0%) and very early timing (47.6%). Relapse varied significantly by risk group (low-risk: 5.9%; intermediate-risk: 10.4%; high-risk: 22.4%; P < 0.001), immunophenotype (B-ALL: 9.8% vs. T-ALL: 23.5%; P = 0.015), Day 19 morphology (M1:9.9% vs. M3:20.0%; P < 0.001), Day 46 morphology (M1:10.5% vs. M3:21.4%; P = 0.025), and Day 46 MRD status (positive:21.4% vs. negative:8.7%; P = 0.002). Fusion gene positivity was significantly associated with earlier relapse timing (P < 0.05). Post-relapse survival differed by relapse timing (very early: 7.2 months; early: 23.2 months; late: 37.8 months; P < 0.001) and initial risk group (low-risk: 38.2 months; high-risk: 18.1 months; P = 0.006).

Non-remission on Days 19/46, Day 46 MRD positivity, and high-risk status predict ALL relapse. High-risk patients experience earlier relapses and poorer survival. Fusion gene positivity is associated with earlier relapse timing.