Acute Myelogenous Leukemia in African American Men: Worse Complete Remission Rate

Abstract & Commentary

Synopsis: In an analysis of seven CALGB acute myelogenous leukemia trials that accrued patients over a 13 year period (1985-1997), complete remission rates and overall survival were found to be worse for African American men, when compared to white men or women or African American women.

Source: Sekeres MA, et al. Blood. 2004;103:4036-4042.

For many cancers, including colon, breast, and prostate, whites have a more favorable prognosis than African Americans in the United States. However, the relationship between race and outcome in leukemia is less apparent. Acute myeloid leukemia (AML) is a malignant disease that develops through the acquisition of genetic mutations in hematopoietic stem or progenitor cells. In the United States, the annual incidence of AML is slightly higher in whites than African Americans (3.7 vs 2.9 cases per 100,000 people). However, currently there is a lack of data comparing incidence and outcome of AML in relation to race or ethnic groups. Differences in cancer outcomes between races are often attributed to several factors including, differential access to care, varying treatment aggressiveness and compliance, as well as biological variability. Sekeres and colleagues from the Department of Hematology and Medical Oncology at The Cleveland Clinic conducted a retrospective cross-sectional analysis of 2570 patients with AML using data from seven Cancer and Leukemia Group B (CALGB) studies that accrued patients between 1985 and 1997. They compared baseline prognostic factors, treatment-related complications, and outcome in white and African American patients receiving similar treatment for AML.

Of the 2570 patients included in the analysis, 270 (10.5%) were African American and 2300 (89.5%) were white. In general, baseline characteristics were similar in the two groups, but African Americans were younger than whites (48 vs 54 years, P < .001). African Americans had different cytogenetic risk group distributions than whites (P < .001). With regard to prognostic grouping based upon cytogenetics, African Americans were more likely to be classified in the favorable (23% versus 14%) and unfavorable (31% vs 23%) groups, and less likely to be classified in the intermediate group (47% vs 63%). In addition, African American men had the lowest complete remission (CR) rate (54% vs 64% for white men, 65% for white women and 70% for African American women, P = .001), and worse overall survival when compared with all other patients (P = .004).

Comment by William B. Ershler, MD

Acute myelogenous leukemia is a heterogeneous group of disorders with varying prognostic features. Thus, certain cytogenetic changes are associated with worse outcomes, and some with better. Similarly, histological features offer prognostic information. When considering the influence of race upon clinical outcomes, an effort to account for these factors is critical. Additionally, outcomes vary on the basis of access to care and treatment offered. Accordingly, the current analysis optimally utilizes a data base for which many of these confounders can be addressed. Patients were referred for CALGB clinical trial, and the population of African Americans included on study was comparable to that in the general population (approximately 10%). Treatments were comparable, and there were sufficient numbers to adjust for cytogenetic and histologic features.

The data indicated in both unadjusted and adjusted analyses that African American men had lover rates of complete remission and overall survival than any other group. This is an important observation, similar to findings for other malignant diseases (colon, breast and prostate cancers).1-3 Similarly, African American children with acute lymphoblastic leukemia are less likely to achieve remission and have an inferior disease free and overall survival.4 In the latter case, at least one study found that African American children were over represented with regard to high-risk prognostic features.5 However, as mentioned, in the current report, analyses revealed a worse outcome for African American men, even after adjustment for prognostic features.

It is possible that some of this difference is artifactual. As the authors suggested, it is possible that post induction therapy (off CALGB trial) might not have been comparable for any of another of reasons, and this might explain differences in overall survival. However, this would not explain the difference in the rate of complete remission, which was found to be lower in African American men. Another factor might be the pattern of referral for clinical trial, although it is difficult to understand any bias in this regard that would influence outcomes under the stringent adjustment analysis undertaken in this evaluation. It is curious that in the current analysis a lower CR rate and worse overall survival was found for African American men, but not African American women. Perhaps there is a clue here.

References

1. Bradley CJ, et al. Cancer. 2001;91:178-188.

2. Marbella AM, Layde PM. Am J Public Health. 2001; 91:118-121.

3. Beart RW, et al. J Am Coll Sug. 1995;181:225-236.

4. Pinkel D. Leukemia. 1993;7(suppl2):S146-S147.

5. Bhatia S, et al. Blood. 2002;100:1957-1964.

William B. Ershler, MD INOVA Fairfax Hospital Cancer Center, Fairfax, VA; Director, Institute for Advanced Studies in Aging, Washington, DC, is Editor of Clinical Oncology Alert.