Complete remission in acute promyelocytic leukemia despite the persistence of the 15;17 translocation

Acute promyelocytic leukemia (APL) is a morphologically distinct subtype of acute non-lymphocytic leukemia (ANLL) characterized cytogenetically by the presence of a translocation between chromosomes 15 and 17 (t(15;17]. In contrast to other subtypes of ANLL, morphologic examination of the bone marrow in the early postinduction period fails to identify patients adequately who have a high likelihood of entering remission. Remission has frequently been achieved in APL despite the failure to attain marrow aplasia or eliminate dysplastic progranulocytes after initial induction chemotherapy. In a patient with APL who failed to achieve cytoreduction after a single course of induction chemotherapy, serial cytogenetic studies demonstrated persistence of metaphases with the t(15;17) up to 23 days after induction. However, complete morphologic and cytogenetic remission was subsequently attained by day 29 without further therapy. In APL remission may occur even when induction therapy fails to achieve marrow aplasia or to eradicate replicative cells with abnormal karyotype promptly. In order to avoid excessive exposure to toxic therapy, new strategies may be necessary to identify, early in treatment, patients with APL who will require only one course of induction chemotherapy to enter remission successfully.