Methotrexate Therapy of T-cell Large Granular Lymphocytic Leukemia Impact of STAT3 Mutation

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.