Affiliations of authors: Institute of Hematology, Soroka University Medical Center, Beer-Sheva, Israel (IL, IG, RY, OS); Chaim Sheba Medical Center, Tel-Aviv University, Ramat-Gan, Israel (IBB).
Correspondence to: Itai Levi, MD, Institute of Hematology, Soroka University Medical Center, P.O. Box 151, Beer-Sheva, 84101, Israel (e-mail: etail{at}clalit.org.il)
The comprehensive meta-analysis reported by Nathan et al. (1) used comparable methods and produced results similar to those in our recent meta-analysis (2), which dealt with the same group of patients and clinical trials. Despite these similarities, the authors of the two studies reached different conclusions. Nathan et al. concluded that the data did not support the routine use of autologous bone marrow transplantation (ABMT) in adult acute myeloid leukemia patients in first complete remission. Indeed, Nathan et al. concluded that their data supported the use of non-myeloablative chemotherapy for patients who do not have a matched sibling donor because there was no statistically significant difference in overall survival between the treatment groups. By contrast, we believe the data do support the routine use of ABMT in adult acute myeloid leukemia patients in first complete remission. With the current increasing use of peripheral blood stem cells in ABMT, the development of new and safer transplant techniques, and the availability of supportive therapy, toxicity and treatment-related mortality is now substantially lower [i.e., 0%6% (3)] compared with the high rate of 14% reported in 1998 by Cassileth et al. (4). As a result, we expect that disease-free survival and overall survival will be longer for patients who receive ABMT than for those who do not.
To test this assumption, we calculated the expected death rates for the ABMT arms of each of the six studies included in both meta-analyses (1,2). Our calculations were designed to assess three different simulations concerning treatment-related mortality: The first analysis assumed similar death rates in both groups (ABMT versus chemotherapy or no further treatment); the second and third simulations assumed death rates of 3% and 5%, respectively, for patients who received ABMT with peripheral blood stem cells (3). The number of expected deaths in this arm was calculated according to the following formula: (number of patients receiving ABMT) x (assumed percentage of treatment-related mortality) + (actual number of patients who died in complete remission) x (actual death rate of relapsed patients) + (actual number of patients who died during relapse). We then calculated the relative risk (RR) and 95% confidence intervals (CIs) of death among patients in the ABMT arm compared with that among patients in the other treatment arm by dividing the new assumed death rate in the first arm by the actual death rate in the other treatment arm for each study. We used the Mantel-Haenszel test to perform a meta-analysis of the six studies for all three assumptions (5).
Table 1 presents the relative risk of death for the individual studies and for the overall meta-analysis according to the assumed treatment-related mortality rates. For all three assumptions, patients in the ABMT arm had a statistically significantly lower relative risk of death than patients in the other treatment arms. The lowest relative risk of death for all studies, 0.85 (95% confidence interval = 0.77 to 0.94), was found using an assumed treatment-related mortality rate of 3%.
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REFERENCES
1 Nathan PC, Sung L, Crump M, Beyene J. Consolidation therapy with autologous bone marrow transplantation in adults with acute myeloid leukemia: a meta-analysis. J Natl Cancer Inst 2004;96:3845.
2 Levi I, Grotto I, Yerushalmi R, Ben-Bassat I, Shpilberg O. Meta-analysis of autologous bone marrow transplantation versus chemotherapy in adult patients with acute myeloid leukemia in first remission. Leuk Res 2004;28:60512.[CrossRef][ISI][Medline]
3 Gorin NC. Autologous bone marrow transplantation for acute myelocytic leukemia. New Orleans (LA): American Society of Hematology; 1999. p. 11937.
4 Cassileth PA, Harrington DP, Appelbaum FR, Lazarus HM, Rowe JM, Paietta E, et al. Chemotherapy compared with autologous or allogeneic bone marrow transplantation in the management of acute myeloid leukemia in first remission. N Engl J Med 1998;339:164956.
5 Fleiss JL. Combining evidence from fourfold tables. In: Statistical methods for rates and proportions. New York (NY): Wiley; 1981. p. 16187.
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