Clinicobiological Characteristics and Outcomes of Patients with T-Cell Large Granular Lymphocytic Leukemia and Chronic Lymphoproliferative Disorder of Natural Killer Cells from a Single Institution

SIMPLE SUMMARY: T-LGLL and CLPD-NK are two indolent lymphoproliferative syndromes whose main symptoms derive from the cytopenia(s). A proportion of patients harbor STAT3 mutations that appear to play an important role in the pathogenesis of the disease. The aim of our retrospective study was to describe the main clinicobiological characteristics, response to therapy and outcome in a large cohort of T-LGLL and CLPD-NK patients diagnosed at a single institution. The impact of STAT3 mutations on the behaviour of the disease and the survival of these patients compared to the age- and sex-matched general population are also evaluated. For the first time, we show that the survival of patients with these two diseases does not differ from that of a matched general Spanish population, confirming the indolent course of these entities. ABSTRACT: T-cell large granular lymphocytic leukemia (T-LGLL) and chronic lymphoproliferative disorder of natural killer (NK) cells are two infrequent diseases characterized by clonal expansions of cytotoxic T lymphocytes and NK cells, respectively. Somatic mutations of STAT3 are involved in the pathogenesis of these entities. We describe the clinicobiological features, mutational status of STAT3/STAT5B, treatment and outcome of 131 patients. Neutropenia was the most frequent finding at diagnosis, followed by anemia. Concurrent hematological disorders were diagnosed in 37% of patients and autoimmune conditions and solid tumors in 17% and 15%, respectively. All patients who needed treatment belonged to the CD8(+)CD57(+) group. Remarkably, patients included in the CD4(+) group had a higher association with solid tumors (p = 0.037). STAT3 mutations were found in 17% of patients, mainly Y640F and D661Y mutations. Patients carrying STAT3 mutations more frequently presented with anemia, neutropenia, high LDH, high large granular lymphocyte counts and need for treatment (p = 0.0037). Methotrexate was the most frequently used agent (72% of cases). The overall response rate to all treatments was 50%. The 10-year overall survival of this series was 78%, with no differences according to the mutational status of STAT3. We compared the survival of these patients with the general Spanish population and no differences were found, confirming the indolent nature of these hematological malignancies. Our study further extends findings documented by others on the clinical behavior of the disease and the impact of STAT3, and for the first time analyzes survival compared to a matched general Spanish population.