Acute lymphoblastic leukemia following preleukemic syndromes in adults

Preleukemic syndromes (PLS) evolve to acute myeloid leukemia (AML) in 15-50% of cases, but rarely transform to acute lymphoblastic leukemia (ALL). AML following preleukemic syndromes has a poor prognosis, but little is reported about the outcome of secondary ALL. From the adult leukemia database at MD Anderson Cancer Center, nine patients with ALL following myelodysplastic syndrome (MDS) (n = 6), smoldering leukemia (n = 1), or cytopenias with dysplastic features (n = 2) were identified. Clinical and laboratory features were abstracted from the database, patient charts, review of the bone marrows and special laboratory studies. The median interval from diagnosis of PLS to ALL was 6 months. Blasts with lymphoid morphology and terminal deoxynucleotidyltransferase (TdT) and periodic acid Schiff (PAS) staining were present in eight of nine cases and four of six cases respectively. T cell and myeloid markers were expressed in the majority of cases, but T cell gene rearrangements were not detected. Only one patient had electron microscopic myeloperoxidase-positive staining. Two patients later transformed to AML. Patients were predominantly male (89%) with a median age of 69 years. The complete remission (CR) rate with ALL-directed chemotherapy (78%) was comparable to that of other adult ALL patients (74%) (n = 327) without excess myelosuppression. Marrow dysplasia persisted in CR in three of seven cases. The median remission duration of 16 months (range 4.5 to 51+ months) and the median overall survival of 21 months (range 1 to 55+ months) were comparable to that of ALL patients overall. ALL following preleukemic syndromes is a distinct syndrome with T cell and myeloid markers and responds well to ALL-directed therapy. The presence of myeloid and lymphoid markers suggests the transformation of an early stem cell.