Relapse, Mortality, and the Associated Factors in Children with Acute Lymphoblastic Leukemia; A Competing Risks Analysis

Background: Acute lymphoblastic leukemia (ALL) is the most frequent form of malignant neoplasia diagnosed in ages 0 to 14 years old. Efforts have not yet converted into a better prospect. Bone marrow relapse is still the leading cause of person-year of life lost in this malignancy. Objectives: This study aimed at identifying the associated risk factors for relapse and mortality for pediatric patients with ALL in standard and high-risk groups. Methods: This study included a cohort of pediatric (0 - 16 years old) patients with ALL referred to Sheikh Hospital, Mashhad, Iran from 2007 to 2016. The demographic, clinical, and laboratory information were considered. Hazard ration (HR) with 95% highest posterior density region was obtained, using a Bayesian competing risks model. Results: Of 424 patients with a mean age of 5.56 ± 3.75 years, 172 (40%) were female. Median follow-up time was 43.29 months, 10.6% had a relapse, and 17.2% had mortality related to ALL. Relapse-free survival rates at 1, 3, and 5 years were 97, 91, and 88%, respectively. Overall survival rates were 86, 83, and 82%, respectively. In the standard-risk group, tumor lysis syndrome (TLS) significantly increased either the relapse risk [HR: 13.47 (2.05 - 67.54)] or mortality risk [HR: 19.57 (2.24 - 32.18)]. In the high-risk group, the higher level of hemoglobin, platelet, and lactic acid dehydrogenase was significantly associated with higher relapse risk. TLS was associated with a higher risk of mortality in high-risk groups. Conclusions: It was suggested that TLS was a predictor for the disease relapse as well as mortality in pediatric patients with ALL. However, further evaluation on the larger population of patients is demanded to ascertain the precision of such parameters in leukemic management strategies.