Background: The poor prognosis for elderly patients with acute myeloid leukemia (AML) raises questions regarding the benefit of treating them with intensive chemotherapy. The impact of initial characteristics on prognosis has been addressed previously in elderly patients; however, very few data are available regarding the prognostic value of immunophenotypic characteristics in this setting.
Methods: The authors investigated expression of the membrane antigens CD13, CD15, CD33, and CD34 by flow cytometry in elderly patients with newly diagnosed AML and analyzed whether these parameters had clinical or prognostic relevance to help physicians in their choice of therapy.
Results: Immunophenotyping was performed in 273 patients aged > or =60 years (median age, 69 years). CD13 was expressed in 73% of patients, CD15 was expressed in 43% of patients, CD33 was expressed in 64% of patients, and CD34 was expressed in 66% of patients. Complete remission was obtained in 157 patients (58%). The median overall survival was 8.1 months, and the 3-year survival rate was 14%. Three risk groups were defined based on CD34 and CD33 antigen expression: The poor-risk group included patients with CD34-positive/CD33-positive or CD34-negative/CD33-negative disease, the intermediate-risk group included patients with CD34-positive/CD33-negative disease, and the favorable-risk group included patients with CD34-negative/CD33-positive disease. After cytogenetic analyses, immunophenotype was the most significant prognostic factor in terms of survival in a multivariate analysis (P = .03 and P < .0001, respectively). When immunophenotypic and cytogenetic parameters were combined, patients were classified into 4 prognostic groups: Group A (3-year survival rate, 33%) included patients with favorable and normal karyotypes who had a favorable immunophenotype, Group B (3-year survival rte, 28%) included patients with normal karyotypes who had an intermediate immunophenotype, Group C (3-year survival rate, 8%) included patients with intermediate or normal karyotypes who had an unfavorable immunophenotype, and Group D (3-year survival rate, 2%) included all patients who had unfavorable cytogenetics.
Conclusions: Immunophenotypic characteristics appeared to be a major prognostic factor in this population of elderly patients with AML. By using 2 simple parameters assessed at the time of diagnosis, the authors devised a prognostic system of immediate clinical utility for prognostic stratification and risk-adapted therapeutic choices.