Characteristics and Survival Outcome Analysis of Extramedullary Involvement in Adult Patients With t(8;21) Acute Myeloid Leukemia.

BACKGROUND: Acute myeloid leukemia (AML) with t(8;21)(q22;q22) is classified into a favorable-risk group. Extramedullary (EM) involvement has frequently been reported in this subgroup as resulting in a poor prognosis. However, characteristics or standard treatments of t(8;21) AML with EM involvement (EM-positive t(8;21)) have not yet been elucidated.

PATIENTS AND METHODS: We retrospectively analyzed 154 adult AML patients with t(8;21). Among them, 17 were EM positive and 137 were EM negative at the time of diagnosis. EM involvement was evaluated only when a patient showed suspicious signs or symptoms. All EM-positive patients were treated according to a strategy based on allogeneic hematopoietic cell transplantation (allo-HCT).

RESULTS: Central nervous system was the most frequently involved site (70.6%). EM-positive t(8;21) was associated with age ≤ 45 years, leukocytosis (≥ 30 × 109 /L), and c-kit mutation compared to EM-negative t(8;21) in multivariate analysis. After intensive chemotherapy with or without local therapy, high-risk t(8;21) AML including EM-positive t(8;21) underwent allo-HCT for postremission therapy. Three-year OS (52.3% vs. 60.0%, P = .658) and event-free survival (51.5% vs. 58.0%, P = .496) were not different between the 2 groups. The subgroup of patients who underwent allo-HCT also showed similar outcomes.

CONCLUSION: EM-positive t(8;21) was associated with young age, leukocytosis, and c-kit mutation, and central nervous system was frequently involved. Allo-HCT resulted in good outcomes in EM-positive t(8;21).