Late Relapse of Acute Promyelocytic Leukemia (FAB M3) in Childhood

—Characteristic Therapeutic Results of M3 Compared to Other Types of Non-lymphocytic Leukemia—

Abstract

During the past 6 years from 1981 through 1986, a total of 33 new cases of childhood acute non-lymphoblastic leukemia (ANLL) were treated with an intensive multi-drug chemotherapy at the Department of Pediatrics, Kyoto Prefectural University of Medicine and other affiliated pediatric clinics.
Excluding 2 cases still receiving early induction therapy, 24 of the remaining 31 cases (78%) attained complete remission (CR); a half of which relapsed or died within 15 months, but another half had, or has been in continuous complete remission (CCR) for over 24 months after beginning of the induction therapy.
All of the 5 M3 patients attained CR and had or has been in CCR over 24 months, indicating that M3 cases easily achieve long term CR. On the other hand, 19 of the other 26 ANLL cases attained CR but only 7 cases had or has been in CCR over 24 months. However, late relapse after 24 months occurred in 3 of the 5 M3 cases, compared with 1 in the 7 other ANLL cases.
Our results may suggest that protocols for M3 cases should be modified to include more intensified, and long-duration maintenance chemotherapy, in order to prevent late relapse.