Clinical characteristics and outcome of isolated extramedullary relapse in acute leukemia after allogeneic stem cell transplantation: a single-center analysis.

Isolated extramedullary relapse (EMR) of acute leukemia (AL) is a rare occurrence. However, it appears to be more common after allogeneic stem cell transplantation (allo-SCT). To characterize what has been observed in isolated EMR, we investigated 287 consecutive AL patients (144 acute myeloid leukemia; 138 acute lymphocytic leukemia; 5 acute mixed-lineage leukemia) who underwent allo-SCT. Twelve cases experienced relapse at extramedullary sites without concomitant involvement of the bone marrow (BM). The onset to relapse after allo-SCT was longer in extramedullary sites than in the BM (median, 10 months versus 5.5 months). EMR sites varied widely and included the central nervous system, skin, bone, pelvis and breasts. Univariate analysis demonstrated that cytogenetic abnormalities were correlated significantly with the onset of isolated EMR (P=0.001). The prognosis for patients who develop EMR remained poor but was relatively better than that after BM relapse (overall survival, 10 versus 18 months). Compared with local or single therapy, patients treated with systemic treatment in combination with local treatment could yield a favorable prognosis. In conclusion, we observed a significant number of isolated cases of EMR in AL patients after allo-SCT, cytogenetic abnormalities were correlated significantly with the onset of isolated EMR. We found that intensive approaches combining local and systemic therapy could produce favorable responses which may cure a proportion of these patients.