Expression of CD56 Is an Independent Prognostic Factor to Predict Relapse in Acute Myeloid Leukemia with t(8;21): Results of Japan Adult Leukemia Study Group (JALSG) AML97 Protocol.

Although prognosis of acute myeloid leukemia (AML) with t(8;21) is better than other types of AML, outcome of the patients has not been satisfied. Previously, aberrant antigen expression has been reported as risk factor for AML with t(8;21). However, in the reported series, number of cases was not large enough and chemotherapy regimens were variable. We investigated the association of prognosis and several biomarkers including immunophenotype, WBC count, age, and performance status for large number of AML patients with t(8;21) uniformly treated in JALSG AML97 regimen.

Seven hundred eighty-nine eligible AML patients were evaluated for the multicenter JALSG AML97 study. Adult patients with de novo AML except for APL, ages 15–64 years, were registered consecutively from 103 institutions that participated in JALSG from December 1997 to July 2001. One hundred forty-four patients with AML with t(8;21) were analyzed in this study with a median 1205 days of observation term from diagnosis. Complete remission (CR), relapse-free survival (RFS), and overall survival (OS) rates were analyzed by Fisher's exact test and log-rank test. Factors that would affect clinical outcome were analyzed by multivariate Cox proportional hazard regression model.

AML with t(8;21) frequently expressed CD19, CD34, and CD56 compared to other subtypes of AML. CD11b was rarely expressed. Expression of CD19 favorably affected on CR rate (96% in CD19 positive and 87% in negative patients, p<0.05). Univariate analysis showed WBC>20×10⁹/L, CD19 negativity, and CD56 positivity were adverse factors for RFS. CD56 expression was the only independent adverse factor for RFS by multivariate analysis (73.7% in CD56 negative and 48.2% in CD56 positive patients at 3 yrs) although its expression did not affect on OS. There was no difference of age, sex, WBC count, presence or absence of Auer rod, performance status, or CD15 expression between CD56 positive and negative cases. Expression of CD19 was more common in CD56 negative patients (50% in CD56 negative and 30.6% in CD56 positive patients, p<0.05).

We demonstrated that the expression of CD56 was a distinctive adverse factor in a large number of AML patients with t(8;21) treated with JALSG AML97 regimen. CD56 positive AML patients with t(8;21) are possible candidates for hematopoietic stem cell transplantation.

No relevant conflicts of interest to declare.