Prognostic factors and treatment effects on survival in acute myeloid leukemia of M6 subtype: A retrospective study of 54 cases

Background: Since 1976, erythroleukemia has been included within the FAB cl assification system of acute myeloid leukemia (AML) which designates it as M6 AML. This report describes the data of 54 patients with newly diagnosed M6 AML, consecutively seen in our hospital between May 1976 and May 1999. Patients and methods: There were 40 males and 14 females. Median age was 59 years. Pancytopenia was the most common feature at diagnosis. Twenty-six p ercent of cases presented with secondary AML. Karyotype was successfully pe rformed in 35 cases. Eleven patients presented with normal karyotype, nine with simple karyotypic abnormalities, and fifteen with major karyotypic abn ormalities. Fifty of the fifty-four patients received one or two courses of induction chemotherapy combining anthracyclines with cytarabine according to different successive protocols. One elderly patient only received low-do se cytarabine, and three patients died before any chemotherapy could be giv en. Results: Complete remission (CR) was achieved in 29 cases (54%, 95% confide nce interval (CI): 40%-67%). As post-remission therapy, four patients could be allografted, and two underwent autologous transplantation. All other tr eated patients received continuation chemotherapy. Twenty-one patients have relapsed (72%). Median time to relapse was six months. Among those patient s, only eight achieved a second CR (38%). The median disease-free survival (DFS) was eight months (95% CI: 4-10 months) with a five-year survival rate of 17%. Median overall survival (OS) was nine months (95% CI: 5-12 months) with a five-year survival rate of 13%. In univariate analysis, poor progno stic factors for DFS were secondary AML (P = 0.05) and initial platelet cou nt < 50 x 109/l (P = 0.02). Poor prognostic factors for OS were age greater than or equal to 60 years (P = 0.005), secondary AML (P = 0.05), initial ' blastic' fever (P = 0.0004), and initial haemoglobin level < 90 g/l (P = 0. 03). All factors, but haemoglobin level, remained significant in the multiv ariate analysis. Although it was not statistically significant, there was a trent for a better prognosis of M6 patients presenting with normal karyoty pe as compared to those displaying chromosomal abnormality. Conclusions: This retrospective analysis points to a somewhat heterogenous group of AML in terms of clinical and biological features, and outcome. Dis tinctive subgroups can be identified according to prognostic factors relate d to survival. A larger multicenter study with well-defined diagnostic crit eria is warranted to further clarify treatment effects.