T-cell large granular lymphocytic leukemia (T-LGLL) is a rare lymphoproliferative disorder and can cooccur in the context of pure red cell aplasia (PRCA). The aim of the current study was to analyze the signal transducer and activator of transcription 3 (STAT3) mutation status and its clinical significance in T-LGLL. We found STAT3 mutations in 21.4% of patients with T-LGLL. High β2-MG (β2-microglobulin) levels (P = 0.005), neutropenia (P = 0.018) and PRCA (P = 0.001) all displayed a significant association with STAT3 mutations. In univariate analysis, treatment-free survival (TFS) was affected by STAT3 mutation status (P = 0.008) and β2-MG (P = 0.006). Our results demonstrate the remarkable correlation of STAT3 mutation with PRCA, neutropenia and β2-MG.

Dasatinib is a second generation tyrosine kinase inhibitor (TKI) approved for clinical use in patients with imatinib-resistant chronic myeloid leukemia (CML) and Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph(+) ALL). Large granular lymphocytes (LGLs) are medium to large cells with eccentric nuclei and abundant cytoplasm with coarse azurophilic granules. LGL lymphocytosis is caused by a proliferation of cytotoxic (CD8+) T cells and/or NK cells. In a proportion of CML and Ph(+) ALL patients, there is a significant expansion of LGLs during dasatinib therapy. LGL lymphocytosis is seen in some cases with fevers, colitis, and pleural effusions (PE), suggesting an aberrant immune response mediated by these LGLs. LGLs may participate in the elimination of the residual leukemic cells, and LGL clonal expansion is associated with excellent, long-lasting therapy responses in dasatinib-treated patients. For a more comprehensive analysis, we analyzed the morphologic, phenotypic, clinical, and functional features of the LGL subsets amplified in vivo during dasatinib therapy.

T-cell large granular lymphocytic leukemia (T-LGLL) is a rare haematologic neoplasm. Consequntly, there are no large prospective studies of therapy and no uniform therapy recommendations. We analyzed data from 36 subjects receiving methotrexate alone (N = 27) or with prednisone (N = 9) as initial therapy. 31 subjects responded (86%, 95% confidence interval [CI], 73, 95%) with 8 complete responses and 23 partial responses. Median time-to-response was 3 months (range, 1–5 months). Median response duration was 20 months (range, 2–55 months). β2-microoglobulin (β2-MG) and erythrocyte sedimentation rate (ESR) decreased significantly post-therapy (P < 0.0001). Pure red cell aplasia (PRCA) was present in 18 subjects (50%) of our subjects and responded well to methotrexate. 26 subjects (72%) were tested for STAT3 mutation. 9 with a mutation had a median treatment-free survival of 5 months (range, 0.5–13 months), significantly briefer than that of 17 subjects without a STAT3 mutation (19 months, range, 3–97 months; P = 0.012; log-rank test). Methotrexate with or without prednisone is an effective initial therapy of persons with T-LGLL with wild-type STAT3.