Abstract: BackgroundMercaptopurine (6-MP) is the core drug during the maintenance treatment of lymphoblastic lymphoma (LBL). 6-methylmercaptopurine (6-MMPN) is an intermediate metabolite of 6-MP, which is thought to be closely related to hepatotoxicity of 6-MP. Foreign studies have shown that the combination of allopurinol may reduce hepatotoxicity ObjectiveTo evaluate whether allopurinol combined with a reduced dose of 6-MP can alleviate the hepatotoxicity of 6-MP during maintenance therapy in children with LBL. DesignCase series report. MethodsAge, gender, clinical stage, liver function, and 6-MP related drug gene of LBL in children with liver function impairment during maintenance therapy from June 2021 to June 2022 in the Department of Oncology, Beijing Children's Hospital Affiliated to Capital Medical University were collected. The changes in liver function, disease status, and other adverse reactions other than liver damage after receiving allopurinol were analyzed retrospectively. Main outcome measures Liver function, the number of weeks that absolute value of neutrophil (ANC) reached standard. ResultsBefore receiving allopurinol, all 17 children had abnormal liver function tests (LFTs). The initial ALT fluctuation was 281.5（200.6-618.0）U·L-1, and AST 118.8（88.2-185.8）U·L-1. After allopurinol administration, ALT was 32.8（27.7-36.75）U·L-1, and AST was 31.8（23.7-36.8）U·L-1, and the time for ALT and AST to return to normal after allopurinol was 6(1,18) weeks and 7 (3,11)weeks, respectively. There was a significant difference in ALT and AST before and after the addition of allopurinol (P<0.01). The ratio of ANC compliance weeks to total maintenance treatment period before and after combination with allopurinol was 21.4% and 34.2%, respectively, with statistical significance (P< 0.001). No neutrophil deficiency fever occurred in the patients. ConclusionThe combination of allopurinol during maintenance treatment in children with LBL treated with 6-MP can effectively reduce their hepatotoxicity and ensure the continuous application of 6-MP. It is safe and effective with controlled adverse reactions.

Key words: 6-Mercaptopurine, Allopurinol, Hepatotoxicity, Lymphoma, Lymphoblastic, Children