Clinical features and long-term prognostic analysis of relapsed pediatric acute lymphoblastic leukemia

Abstract

Objective: To investigate the clinical characteristics and long-term prognostic factors of relapsed pediatric acute lymphoblastic leukemia (ALL). Methods: Clinical data including the age, time from initial diagnosis to relapse, relapse site, and molecular biological features of 217 relapsed ALL children primarily treated by the Chinese Children's Leukemia Group (CCLG)-ALL 2008 protocol in Institute of Hematology & Blood Diseases Hospital, Chinese Academy of Medical Sciences between April 2008 and April 2015 were collected and analyzed in this retrospective cohort study. Kaplan-Meier analysis was used to evaluate the overall survival (OS) rate and event free survival (EFS) rate for univariate analysis, and Cox proportional-hazards regression model was used to evaluate the influencing factors of OS rate and EFS rate for multivariate analysis. Results: The age at initial diagnosis of 217 relapsed patients was 5 (3, 7) years. There were 135 males and 82 females. The time from initial diagnosis to relapse of 217 children was 22 (10, 39) months. After relapse, 136 out of 217 children (62.7%) received treatment and the follow-up time was 65 (47, 90) months. The 5-year OS rate and EFS rate of the 136 relapsed children were (37±4) % and (26±4) %, respectively. The predicted 10-year OS rate and EFS rate were (35±5) % and (20±4) %, respectively. Univariate analysis showed that the 5-year OS rate in the group of patients with late relapse (43 cases) was significantly higher than those with very early (54 cases) and early relapse (39 cases) ((72±7)% vs. (16±5)%, (28±8)%, χ2=35.91, P<0.05), 5-year OS rate of the isolated extramedullary relapse group (20 cases) was significantly higher than isolated bone marrow relapse group (102 cases) and combined relapse group (14 cases) ((69±11)% vs. (31±5)%, (29±12)%, χ2=9.14, P<0.05), 5-year OS rate of high-risk group (80 cases) was significantly lower than standard-risk group (10 cases) and intermediate-risk group (46 cases) ((20±5)% vs. (90±10)%, (54±8)%, χ2=32.88, P<0.05). ETV6::RUNX1 was the most common fusion gene (13.2%, 18/136). The predicted 10-year OS rate of relapsed children with positive ETV6::RUNX1 was significantly higher than those without ETV6::RUNX1 (118 cases) ((83±9)% vs. (26±5)%, χ2=14.04, P<0.05). The 5-year OS for those accepted hematopoietic stem cell transplantation (HSCT) after relapse (42 cases) was higher than those without HSCT (94 cases) ((56±8)% vs. (27±5)%, χ2=15.18, P<0.05). Multivariate analysis identified very early/early relapse (HR=3.91, 95%CI 1.96-7.79; HR=4.15, 95%CI 1.99-8.67), bone marrow relapse including isolated bone marrow relapse and combined relapse (HR=6.50, 95%CI 2.58-16.34; HR=5.19, 95%CI 1.78-15.16), with ETV6::RUNX1 (HR=0.23, 95%CI 0.07-0.74) and HSCT after relapse (HR=0.24, 95%CI 0.14-0.43) as independent prognostic factors for OS (all P<0.05). Conclusions: Relapsed pediatric ALL mainly occurs very early and often affects bone marrow, which confer poor outcome. ETV6::RUNX1 is the most common genetic aberration with a favorable outcome. HSCT could rescue the outcome of relapsed children, though the survival rate is still poor.