EXTRAMEDULLARY RELAPSE AFTER FAVORABLE MOLECULAR RESPONSE TO DONOR LEUKOCYTE INFUSIONS FOR RECURRING ACUTE-LEUKEMIA

Donor leukocyte infusions (DLI) have fumed out to be an efficient way to re-establish complete remission (CR) in chronic myeloid leukemia (C ML) patients relapsing after allogeneic bone marrow transplantation (B MT). In these patients, absence of PCR bcr-abl fusion transcripts conf irmed the potency of donor leukocytes to induce molecular response in relapsed CML. This ensured sustained remission and long-term survival. In this study, the capacity of DLI to induce molecular remission in a cute leukemia relapse after BMT was analyzed. The results showed that following DLI, leukemic cell eradication gradually occurred over a pro longed time period. The time to complete disappearance of the molecula r marker of the disease was 30 weeks in RT-PCR analysis. A sustained a nd persistent elimination of an AML1/ETO-positIve leukemic clone in an AML-M-2 patient was observed. In contrast, an AML-M-5 with t(11;19) a nd an E2A/PBX1-positive ALL achieving cytogenetic and molecular bone m arrow CR developed following DLI unusual sites of extramedullary leuke mia relapse, despite continued bone marrow remission. This study adds further proof of the benefit of donor cell therapy in acute leukemia b ut shows that complete leukemic cell eradication appears to require a critical interval in order to establish effective immune responses at all sites where leukemic cells persist.