Clinical Manifestations, Prognostic Factors, and Outcomes of Extranodal Natural Killer T-Cell Lymphoma: A Single-Center Experience in Thailand

<b>Background/Objectives</b>: The primary objective of this study was to investigate clinical manifestations, time to diagnosis, and number of biopsies in patients with extranodal natural killer T-cell lymphoma (ENKTL). The secondary objectives were to determine response rates, survival outcomes, prognostic factor for overall survival (OS), and validation of the Prognostic Index of Natural Killer Lymphoma (PINK), Ann Arbor staging system (AASS), and the CA system. <b>Methods</b>: This retrospective study included data pertaining to patients with newly diagnosed ENKTL in Chiang-Mai University Hospital from 2004 to 2020. Comparisons between the areas under the receiver operating characteristic curve (AUC) of prognostic models (PINK, AASS, and CA system) were made. <b>Results</b>: Sixty patients were enrolled (n = 60) with a mean age of 49.1 ± 13.4 years. The most frequent symptom of ENKTL was nasal obstruction (66%). The median time to diagnosis was 22 days (ranging from 3 to 84 days), with 36.7% requiring more than one biopsy for diagnosis. Most patients presented with limited stage disease (75%). The median OS was 49 months. Factors associated with increased mortality were advanced stage, bone marrow involvement, gastrointestinal tract involvement, and receiving chemotherapy. Following prognostic model validation, the CA system model scored the highest level of accuracy (AUC 0.61), followed by AASS (AUC 0.58) and PINK (AUC 0.54). <b>Conclusions</b>: Patients with ENKTL commonly presented with nasal obstruction, with 36.7% requiring more than one biopsy for diagnosis. An advanced stage, bone marrow involvement, or gastrointestinal tract involvement were associated with poor OS. The CA system model has the highest level of accuracy for prognostic determination.