Black Patients with Acute Myeloid Leukemia (AML) Are Younger and More Commonly Female, but Have a Higher Incidence of Complex Karyotypes When Compared to Whites.

Abstract 2649

Poster Board II-625

Racial differences in clinical characteristics and treatment outcomes have been identified in a number of malignancies, but these relationships have not been extensively studied in the adult AML population. A single cooperative group study of a population that included 10% blacks (Sekeres, Blood 2004;103:4036) reported a higher incidence of several translocations, both favorable and unfavorable, as well as more frequent favorable and unfavorable and less frequent normal karyotypes in blacks, compared to whites. This study's goal was to examine the prevalence of karyotype abnormalities and FLT3 mutations in unselected patients of different racial backgrounds treated in our Cancer Center, which is in a large urban medical center with a diverse patient population. Secondary leukemia patients and older patients, who are underrepresented in clinical trials, were included in our study population. We retrospectively reviewed patients with a diagnosis of AML evaluated and treated at the University of Maryland Greenebaum Cancer Center during the years 2000-2009. Cases were reviewed for age, sex, race, de novo or secondary AML onset, karyotype and FLT3 mutation status. Cytogenetic data were categorized into the favorable karyotypes t(15;17), t(8;21), inv(16) or t(16;16), normal and other intermediate karyotypes, and complex (3 or more unrelated numerical or structural cytogenetic changes) and other unfavorable karyotypes by Southwest Oncology Group criteria (Slovak, Blood 2000;96:4075). A total of 498 AML patients were identified. Cytogenetic data were available for 463 patients (93%), and FLT3 data for 153 (31%). Of the patients with available karyotype data, 333 (72%) were white, 91 (20%) black, 19 (4%) Hispanic, and 19 (4%) Asian. t(15;17), defining acute promyelocytic leukemia (APL, FAB M3), was more common in non-whites than whites (16% vs. 7%; p=0.006). As 92% of our population was white or black, further subgroup analysis was limited to differences between these two groups. Blacks presented at a significantly younger age than whites (54.5 years vs. 59.8 years; p<0.001) and were more frequently female (55% vs. 47%; p<0.001). The prevalence of secondary leukemia was similar in blacks and whites (24% vs. 28%). A strikingly higher incidence of complex karyotypes was seen in blacks when compared to whites (28% vs. 13%; p=0.001). When considering only patients with complex karyotypes, black and white patients had a similar age of AML presentation (median 57 vs. 61 years; p = 0.16), but the proportion of women was significantly higher among blacks, compared to whites (64% vs. 39%, p<0.001). The incidence of secondary AML (38% vs. 37%) and of both therapy-related AML (21% vs. 24%) and antecedent hematological disorders (16% vs. 14%) was similar in blacks and whites with complex karyotypes. A similar proportion of black and white patients with complex karyotypes underwent stem cell transplantation (16% vs. 20%). Survival among both black and white patients with complex karyotypes was similarly poor, with long-term survival in only 1 of 25 black patients and 2 of 44 white patients. No other significant differences in karyotype distributions were found between black and white patients, and the frequency of FLT3 mutations did not differ between races when examined across all karyotypes (n= 140, black and white patients) or only in patients with normal karyotypes (n=64, black and white patients). Although black patients with AML in our population presented at a younger age, were more frequently female and had a similar incidence of secondary leukemia, they had a significantly higher incidence of complex karyotypes when compared to white AML patients. Risk factors responsible for this difference remain to be identified.