Tehran University of Medical Sciences Acta Medica Iranica 0044-6025 58 3 2020 07 19 109 114 Gholamreza Bahoush Department of Pediatrics, School of Medicine, Iran University of Medical Sciences, Tehran, Iran. Leila Asgarzadeh Department of Pediatrics, School of Medicine, Iran University of Medical Sciences, Tehran, Iran. Marzieh Nojoomi Preventive Medicine and Public Health Research Center, Psychosocial Health Research Institute, Iran University of Medical Sciences, Tehran, Iran. AND Department of Community and Family Medicine, School of Medicine, Iran University of Medical Sciences, Tehran, Iran. 2019 09 19 2020 04 25 In acute lymphoblastic leukemia (ALL) patients treated with L-asparaginase, discontinuation of the drug occasionally occur due to severe drug complications or resistance, however, due to the high efficacy of this drug in the recovery of patients and the prevention of disease recurrence, resuming the drug regimen is preferred in most patients. What we did in this study was to evaluate and compare the effects of clinical outcomes in the two modes of continuing and discontinuing drug use. In this retrospective cohort study, all children with ALL who had been treated with L-asparaginase during the years 2005 to 2015 were included in the study and categorized into two groups receiving complete treatment regimen (n=160) and those who had to discontinue the drug due to appearing complications (n=9). The rate of relapse and mortality rate was determined and compared across the two groups with a median follow-up time of more than 5 years. 5-yrs Overall survival of all enrolled patients in the groups continued and discontinued was 91.4±2.5% and 71.4±17.1%, respectively (P=0.792). Also, 5-yrs event-free survival of the two groups was 75.8±3.5% and 71.4±17.1%, respectively (P=0.557. Relapse was revealed in 17.5% and 33.3% respectively and mortality in 16.9% and 0.0% (P=0.261). However, the overall prevalence of hypersensitivity reaction to the drug was significantly higher in those patients who discontinued their drug regimen (100% versus 24.4%, P<0.001). Hypersensitivity reaction to drugs may be an important factor in discontinuing L-asparaginase in patients with ALL. The discontinuation of L-asparaginase supplementation due to various complications such as hypersensitivity reactions may be effective in the survival of these patients. However, accurate determination of the effect of discontinuation of this drug on the outcome of children with ALL requires a more comprehensive study with more complicated cases. https://acta.tums.ac.ir/index.php/acta/article/view/8090 https://acta.tums.ac.ir/index.php/acta/article/download/8090/5380