Epstein-Barr Virus-positive NK/T-cell Malignancies in Poland: Distinctive Features, Therapeutic Strategies, and Survival Insights-The Real-world Retrospective Report of the Polish Lymphoma Research Group.

[AIM] Extranodal NK/T-cell lymphoma (ENKTCL) and aggressive NK-cell leukemia (ANKL) are rare aggressive hematologic malignancies. Genetic differences and varying Epstein-Barr virus (EBV) strains suggest potential disparities in disease characteristics in Europe compared to Asian countries. Our aim was to describe clinical characteristics and treatment approaches of these tumors in the solid Polish population.

[MATERIALS AND METHODS] A retrospective analysis of 23 patients diagnosed between 2018 and 2023 across six Polish centers was conducted (20 ENKTCL and three ANKL).

[RESULTS] Mean age was 50.1 years, with 73.9% male. Early stages and low-risk dominated (75%). Common first-line treatments included DeVIC (41%) and asparaginase-based regimens (45%). Rituximab was used in three first-line and two second-line cases. Consolidation with autologous hematopoietic cell transplantation was performed in four and three cases, respectively. The 2-year progression-free survival (PFS) and overall survival (OS) were 57.8% and 75.2%, respectively. Early disease stage and response to the first-line therapy were associated with higher PFS with hazard ratios (HRs) 3.5 (95% confidence interval [CI]: 1.6-8.97) and 1.84 (95% CI: 1.02-3.3), respectively. Hemophagocytic lymphohistiocytosis (HLH) was found in 21.7% of patients and was the strongest predictor of poor OS with HR 10.79 (95% CI: 1.96-59.5).

[CONCLUSIONS] The demographic and clinical characteristics of the Polish patient population were similar to those reported in Asian populations. Approximately 45% of patients received asparaginase-containing regimens. The efficacy of first-line regimens seemed to be lower compared to those reported in the literature. The presence of HLH is the most critical factor predicting poor survival.