CLINICAL AND BIOLOGICAL CHARACTERISTICS OF ACUTE PROMYELOCYTIC LEUKEMIA IN TAIWAN - A HIGH RELAPSE RATE IN PATIENTS WITH HIGH INITIAL AND PEAK WHITE BLOOD-CELL COUNTS DURING ALL-TRANS-RETINOIC ACID TREATMENT

Acute promyelocytic leukemia (APL) patients treated with all-trans ret inoic acid (ATRA) and chemotherapy have been shown to have better outc ome than those treated with conventional chemotherapy alone. However, the biological characteristics of leukemic cells and their clinical im plications in patients treated with ATRA have not been well establishe d. In this study, the biological and clinical features of 30 APL patie nts were reported. The risk factors for relapse and for occurrence of retinoic acid (RA) syndrome, which might cause morbidity or mortality of patients after ATRA treatment, were also analyzed. All patients sho wed 15;17 translocation by cytogenetic and/or gene analysis. Patients in this study had higher white blood cell (WBC) counts and a higher in cidence of additional abnormalities than those from other areas. The r atio of long (L) form to short (S) form PML-RAR alpha fusion transcrip t was 1.8:1, a value lower than that of Latino patients but higher tha n that of Italians. Leukemic cells from four patients showed coexpress ion of T cell-associated antigen CD2 which was highly correlated with S form fusion transcript. Nine (36%) of the 25 patients treated with A TRA developed RA syndrome; all but one were successfully controlled by corticosteroid. Complete remission (CR) rate was 84%. Patients with h igh WBC counts tended to develop RA syndrome and had increased risk of relapse. Isochromosome for the long arm of the derivative chromosome 17, ider(17q), as an additional chromosomal abnormality was also assoc iated with poor outcome in this study. In conclusion, APL in this stud y showed some different biological characteristics compared with those reported in other areas. High WBC count was a risk factor for relapse and development of RA syndrome after ATRA treatment. The prognostic i mplication of the presence of ider(17q) needs further clarification.