Clinical Characteristics and Outcome of Isolated Extramedullary Relapse in Acute Leukemia Following Allogeneic Stem Cell Transplantation: A Single Institutional Analysis

Abstract 4211

Isolated extramedullary relapse (EMR) of acute leukemia (AL) is a rare occurrence although it appears to be more common following allogeneic stem cell transplantation (allo-SCT). To characterize what has been observed in isolated EMR, we investigated a total of 287 consecutive AL patients (144 acute myeloid leukemia, 138 acute lymphocytic leukemia and 5 acute mixed lineage leukemia) who underwent allo-SCT.

Forty-seven (16.4%) patients experienced relapse after allo-SCT. 12 cases (4.2%) experienced relapse of extramedullary sites without concomitant bone marrow involvement. Isolated EMR accounted for 25.5% of the overall initial relapse. The time to relapse after allo-SCT was longer in the extramedullary sites than in the marrow (median, 10 months vs. 5.5 months, P<0.05,). Sites of EMR varied widely including central nervous system, skin, bone, pelvis and breasts. The variables considered for univariate analysis included donor gender, age, primary disease, disease status, cytogenetics/molecular abnormalities, preconditioning regimen, donor type, HLA match, aGVHD and cGVHD. The variables that showed significant correlation with isolated EMR were the cytogenetics abnormalities at diagnosis. The prognosis for patients who develop EMR remained poor but was relatively better than that after bone marrow (BM) relapse (overall survival, 10 vs. 18 months, P<0.05). Compared with local or single therapy, patients treated with systemic in combination with local treatment could yield favorable prognosis. Three patients survived 63, 55 and 49 months after transplant respectively, of whom two received DLI with subsequent chemotherapy and (or) irradiation and one had surgery with subsequent chemotherapy.

In conclusion, we observed a significant number of isolated EMR of AL after allo-SCT and intensive approaches combined of local and systemic therapy can produce favorable response which may cure a percentage of these patients.