Evaluation and Chemotherapy of Residual Disease in Acute Leukemia

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Abstract

During the last fifteen years major progress has been accomplished in the induction treatment of acute leukemia in adults, with about 70 % complete remission (CR), achieved in acute myelogenous leukemia (AML) and in acute lymphoblastic leukemia (ALL), except in old and poor prognostic patients — secondary leukemias, blast crisis —. However in most center the number of long term survivors is still lower than 5 % (30). In our department, only 2 % of the 806 patients referred during the 11 last years are alive in their first CR for more than 4 years. The risk of relapse after a prolonged CR is low: we have observed two such AML patients who relapsed after 5 and 8 years of CR, but this occurs unfreguently — 2.8 % of cases in a large multicentric study (30) —. Extensive histologic examinations have shown a high frequency of occult foci of leukemic cells in various tissues when such surveys were made shortly after the establishment of CR (20), whereas similar studies in ALL patients in continuous CR for three or more years revealed only few positive testicular biopsies (17). One can hypothesize consequently that the leukemic cell burden in most patients in short term CR is relatively high, not far under the 1010 cells corresponding to the limit between overt disease and CR. Cytogenetic studies have shown that most relapses — even after bone marrow allogenic transplant — originate from the initial clone, taking into account clonal evolution and/or subclones expansion. Evaluation and treatment of the residual disease, once a CR is obtained, is therefore actually the major task in the treatment of acute leukemia.