Epidemiology and Survival Determinants of Monomorphic Epitheliotropic T-Cell Lymphoma: A Pooled Patient-Level Dataset Analysis.

Monomorphic epitheliotropic intestinal T-cell lymphoma (MEITL) is a rare, aggressive intestinal T-cell lymphoma with poorly defined prognostic factors and limited therapeutic evidence. This study presents a retrospective, pooled patient-level analysis of MEITL cases, including those previously classified as type II enteropathy-associated T-cell lymphoma, consistent with modern MEITL criteria. Among 299 patients, the median age was 60 years, with a male preponderance. Cases clustered predominantly in East Asia. Abdominal pain was the most frequent presentation, and perforation occurred in 31.9% of cases. The canonical CD3+, CD4-, CD5-, CD8+, CD56+ phenotype was present in 65.9% of fully annotated cases. Median OS was 12 months, and median PFS was 5 months. Elevated LDH ≥ 250 U/L (p = 0.002), advanced Lugano stage II2/IIE/IV (p = 0.042), and non-ileal-only disease distribution were associated with inferior OS, whereas isolated ileal involvement was favorable (p = 0.004). In multivariable analysis, advanced Lugano stage, non-ileal-only involvement, and failure to achieve complete or partial response remained independently adverse. An exploratory prognostic score incorporating stage, anatomic distribution, and LDH showed preliminary risk group separation in a small subset of patients (C-index 0.734). Stem cell transplantation (SCT) was associated with improved survival in fixed-time analyses, but this association was attenuated after accounting for transplant timing; exploratory responder-restricted and landmark analyses suggested that any potential SCT benefit may be concentrated among patients with chemotherapy-sensitive disease. MEITL demonstrates poor survival despite multimodality therapy. Disease extent, anatomic distribution, LDH, treatment response, and response-adapted SCT may inform risk stratification and management.