Outcome of L-DEP regimen for treatment of pediatric chronic active Epstein–Barr virus infection

We intended to investigate the clinical features of paediatric patients with chronic active Epstein-Barr virus infection (CAEBV) and to examine the effectiveness of the L-DEP regimen before haematopoietic stem cell transplantation (HSCT). A retrospective analysis was performed on 35 patients with CAEBV at Beijing Children's Hospital from January 2016 to January 2020. The efficacy and adverse events of the L-DEP regimen were evaluated. The median age of the 35 patients was 7.0 years old (range 2.5-17.5 years). Twenty-eight patients achieved a clinical response (80.0%, 22 in clinical CR, 6 in clinical PR) after L-DEP. In terms of virological response, 7 patients (20%) were assessed as having virological CR, and 23 patients (65.7%) had virological PR. Finally, 29 patients underwent allo-HSCT. The median survival time was 18 months (2-50 months). The 3-year overall survival rates in patients treated with chemotherapy only (n = 6) and chemotherapy followed by HSCT (n = 25) were 33.3% and 75.4%, respectively. After L-DEP 1st treatment and L-DEP 2nd treatment, the EBV-DNA loads in blood and plasma were significantly reduced compared with those before chemotherapy (median: 4.29 x 10.sup.5 copies/ml vs. 1.84 x 10.sup.6 copies/ml, Mann-Whitney U: P = 0.0004; 5.00 x 10.sup.2 copies/ml vs. 3.17 x 10.sup.3 copies/ml, Mann-Whitney U; P = 0.003; 2.27 x 10.sup.5 copies/ml vs. 1.84 x 10.sup.6 copies/ml, P = 0.0001; 5.00 x 10.sup.2 copies/ml vs. 3.17 x 10.sup.3 copies/ml, P = 0.003). Compared with the liver and spleen size before chemotherapy, the size of the liver and spleen shrank significantly after L-DEP 2nd (median 3.8 cm vs. 1.9 cm, P = 0.003; 3.8 cm vs. 0 cm, P < 0.008). In addition, after L-DEP treatment, there was no difference in the clinical or virological response rate regardless of HLH status (clinical response: 77.3% vs. 84.6%, P = 0.689; virological response: 90.9% vs. 76.9%, P = 0.337). The L-DEP regimen is an effective therapy in CAEBV for bridging to allo-HSCT.