Isolated extramedullary relapse in acute myeloid leukemia: A retrospective analysis

Little is known about the characteristics and outcome of children with acute myeloid leukemia (AML) experiencing an isolated extramedullary relapse (IEMR).

The tumor registry of The Children's Hospital of Philadelphia identified 215 patients with AML diagnosed between 1970 and 2000, of which 16 (7.4%) experienced IEMR. Patient- and disease-related features and outcome of patients with IEMR and other patients with AML were compared.

IEMR occurred a median of 4.5 months (1.5-74 months) from diagnosis. Male to female ratio was 4.3:1 in patients with IEMR and 1.1:1 in the other patients with AML (P = 0.048). Median age at diagnosis and median presenting WBC were not significantly different in patients with and without IEMR. Patients with IEMR were more likely to have extramedullary disease (EMD) at diagnosis (31 vs. 4.5%) (P =.002) and FAB M4 or M5 morphology (P =.0001). Leukemic cells in 7 of 13 patients (54%) had t(11q23), inversion 16 or t(8;21) with IEMR compared to 21 of 93 other patients (23%) (P = 0.166). Six of 16 (37.5%) patients survive a median of 4.5 years (range 1.5-15 years) after IEMR and there are 13 survivors (23%) of 57 patients after marrow or combined relapse (P = 0.56). One survivor of IEMR received local irradiation and continued on maintenance therapy while the other five received chemotherapy, irradiation, and allogeneic marrow transplant in second or third remission.

Patients with isolated EMR are typically young males with monoblastic or myeloblastic leukemia who present with EMD at diagnosis. Marrow transplant following chemotherapy and local radiotherapy offer the potential for long-term survival.