Acute Leukemia |
Department of Hematology, Changhai Hospital, Second Military Medical University, Shangai, China
Correspondence: Jian-Min Wang, Department of Hematology, Changhai Hospital, Secondary Military Medical University, 168 Changhai Road, Shanghai 200433, China. E-mail:jmwang{at}medmail.com.cn
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Design and Methods: We retrospectively analyzed 452 adult acute leukemia patients diagnosed according to French-American-British (FAB) classification and biphenotypic acute leukemia diagnosed according to European Group for the Immunological Characterization of Leukemias (EGIL) classification, respectively. Biological characteristics, response to treatment, and outcome were examined in biphenotypic acute leukemia patients and compared with that in acute myeloid leukemia and acute lymphoblastic leukemia patients with complete follow-up profiles diagnosed in the same period.
Results: Of 452 acute leukemia patients, 21 cases (4.6%) were diagnosed as biphenotypic acute leukemia. Among them, 14 (66.7%) were B lymphoid and myeloid, 5 (23.8%) were T lymphoid and myeloid, one (4.8%) was T/B lymphoid and one (4.8%) was trilineage differentiation. When compared with acute myeloid leukemia and acute lymphoblastic leukemia, patients with biphenotypic acute leukemia showed significantly higher incidence of CD34 antigen expression, unfavorable karyotypes, and extramedullary infiltration (p<0.05). In this cohort of patients with biphenotypic acute leukemia, t(9;22) was the most common abnormality in chromosome structure. The median disease-free survival and overall survival in biphenotypic acute leukemia patients was five months and ten months, respectively, significantly shorter than those in acute myeloid leukemia and acute lymphoblastic leukemia patients (p<0.05).
Conclusions: The prognosis of biphenotypic acute leukemia patients is poor when compared with de novo acute myeloid leukemia or acute lymphoblastic leukemia. Biphenotypic acute leukemia patients showed a much higher incidence of CD34 antigen expression, complex abnormal karyotype, extramedullary infiltration, relapse, and resistance to therapy after relapse.
Key words: biphenotypic leukemia, immunophenotype, cytogenetics, prognosis.
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Immunophenotyping
Flow cytometry immunophenotyping was performed on fresh bone marrow or blood specimens. Single-cell suspensions were incubated with combinations of monoclonal antibodies in two or four-color immunofluorescence using concentrations titrated for optimal staining. Antibodies used in the analysis recognized stem cell and panleukocyte antigens including CD45, CD34, CD38, TdT, and HLA-DR; myeloid-associated antigens including myeloperoxidase (MPO), CD117, CD33, CD13, CD14, CD15, and CD64; and lymphoid-associated antigens, including surface and cytoplasmic CD3, CD5, CD7, CD2, CD4, CD8, CD10, CD19, CD20, CD22, CD9, CD79a, and CD56. The myeloid or B/T lymphoid makers were considered to be positive if they were expressed in >20% of blasts.
Morphology and cytochemical analysis
Bone marrow aspiration occurred under Wright Geimsa staining, and 200 cells were analyzed, along with myeloperoxidase, non-specific esterase stain, sodium fluoride inhibition tests, and periodic acid Schiff reactions for cytochemical assay. One hundred Giemsa-stained peripheral blood cells were analyzed.
Cytogenetic analysis
Direct and short-term culture methods were applied in preparation of bone marrow specimens. Chromosome banding was carried out by heating using the Giemsa (RHG) method, with an average of 20 metaphase cells analyzed in each case. Karyotype was determined according to the International System for Human Cytogenic Nomenclature (ISCN, 1995). Unfavorable karyotypes were defined as t(9,22) or abnormalities of chromosomes 5 or 7, abnormalities of chromosome 11q23, and complex abnormalities (
3 types).
Treatment
Induction
Induction therapy included the DA (daunomycin 45 mg/m2 d 1–3, cytarabine 150 mg/m2 d 1–7) protocol for most AML patients and VDCPL (vincristine 1.5 mg/m2d,1,8,15,22 daunorubicin 45 mg/m2 d,1-3,15–17 cyclophosphamide 0.8 g/m2 d,1,15 prednisolone 40 mg/m2 d,1–28 and asparaginase 6000 units/m2 d 19–28) protocol for most ALL patients. The induction protocol for patients with BAL is listed in Table 1. Three different regimens were adopted in our study. Five cases received DA protocol for myeloid lineage. Six patients received VDCPL protocol. The other 10 patients received VPDA protocol for both myeloid and lymphoid lineages.
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Table 1. Induction therapy, post-remission therapy, and salvage therapy after relapse, overall survival, and disease free survival of patients with biphe-notypic acute leukemia.
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Follow-up
All patients were followed-up from diagnosis of the disease until the end of May 2008. The median follow-up period was 37 months (range, 12-85), 45 months (range, 12–89), and 46.5 months (range, 15.5–89) for BAL, AML, and ALL, respectively.
Statistical methods
Mann-Whitney U tests were used for comparison of numerical values.
2 or Fishers exact tests were used for categorical comparison of small expected values. Kaplan-Meier survival curves were used to compare survival rates. Differences between the curves were examined statistically using the log rank test and derivatives. All data show as median (range) and differences were considered significant at the p<0.05 level. Statistical analysis was performed using SPSS 11.0.
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Table 2. Scoring system for the definition of biphenotypic acute leukemia.
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Table 3. Immunological markers of 21 patients with biphenotypic acute leukemia.
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Table 4. General information, peripheral white blood cell count, and karyotype of patients with biphenotypic acute leukemia.
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Survival analysis
Univariate analysis of OS including clinical manifestations and laboratory tests showed that age, WBC count, extramedullary infiltration, primary induction treatment, and whether or not patients achieved CR after induction, were significantly related to patients prognosis.
Comparison of biphenotypic acute leukemia and acute myeloid leukemia in clinical and biological features
Comparison of BAL and 191 AML patients was carried out as shown in Table 5, excluding patients lost to follow-up and M3 subtype because of its particular biological features. Significant differences were noted in CD34 positive rates, incidence of karyotype abnormalities, t(9;22), complex karyotypes, unfavorable karyotypes and extramedullary infiltration (p<0.05).
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Table 5. The overall review of the clinical features and outcome of patients with biphenotypic acute leukemia, acute myeloid leukemia, and acute lymphoid leukemia.
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Comparison of the response to treatment and outcomes between acute myeloid leukemia, acute lymphocytic leukemia, and biphenotypic acute leukemia
Responses to treatment and outcomes in BAL patients were compared with those of AML and ALL (Table 5) diagnosed in the same period. No statistical difference was noted in CR rate after the first induction and overall CR rate (p>0.05). The incidence of relapse in BAL patients was significantly higher than that of patients with AML, while CR rates after relapse were lower in BAL patients than those with AML (p<0.05). A significant worse OS and DFS for BAL when compared with that of ALL (p=0.0003, p=0.007)and AML (p=0.0044, p=0.0119) is denoted by the Kaplan-Meier curve (Figure 1). ALL and AML patients had better outcome than BAL patients (Figure 1). The OS (p=0.000 and p=0.013, respectively) as well as DFS (p=0.002 and p=0.007, respectively) of patients with AML and ALL was significantly higher than that of BAL after relapse (Figure 2).
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Figure 1. (A) The overall survival of patients with BAL (solid line), AML (dashed line) and ALL (dotted line). The survival time was analyzed by Kaplan-Meier curve. (B) The disease free survival of patients with BAL, AML and ALL. The survival time was analyzed by Kaplan-Meier curve. The x-axes are the survival time and y-axes are cumulative survival.
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Figure 2. (A) The overall survival of patients with BAL (solid line), AML (dashed line) and ALL (dotted line) after relapse. The survival time was analyzed by Kaplan-Meier curve. (B) The disease free survival of patients with BAL, AML and ALL after relapse. The survival time was analyzed by Kaplan-Meier curve. The x-axes are the survival time and y-axes are cumulative survival.
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Table 6. Clinical and biological features of patients with biphenotypic acute leukemia in different studies.
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Additionally, we also reported 2 cases with t(8;21). AML with t(8;21) translocation is classified as a unique category (recurrent cytogenetic translocation) according to WHO classification (2001). Although the 2 patients with t(8;21) translocation in our study were diagnosed as AML-M2 based on pathological morphology, the myeloid and B-lymphoid markers were all positive in immunophenotyping. So we included these 2 patients in BAL. He et al.21 also reported 6 cases of B-lymphoid and myeloid lineages BAL with t(8;21)(q22;q22). By analyzing the characteristics of morphology, immune phenotype, chromosome karyotype and clinical manifestations of these 6 cases, they considered that BAL with t(8; 21)(q22;q22) might be a new subgroup of BAL. Miyamotos findings suggested that the acquisition of the t(8;21) occurs at the level of stem cell, capable of differentiating into B cells as well as all myeloid lineages.22 The survival times of 2 patients with t(8;21) in our series were 1.5 and 7 months, which were shorter than those of AML patients with t(8;21) (median survival time 22 months, p<0.05). We hypothesized that: (i) the particular biological and clinical features of BAL should be taken into consideration, i.e., t(8;21) is not a favorable indication of good prognosis in BAL, and (ii) these 2 patients also had other abnormal chromosome structures, which were classified as complex abnormalities.
The univariate analysis of prognosis in our study showed that the prognosis of patients with BAL was significantly related to age, peripheral WBC count, extramedullary infiltration and whether or not patients achieved CR after induction. But due to the small numbers of cases, its still difficult for us to draw any conclusion from our series. A multi-center and perspective clinical study will be critical to have a wider picture of this rare disease.
Treatment of BAL is complicated and problematic. In our series, the overall CR rate was 71.4%. There was no statistical difference when comparing with AML and ALL (p>0.05). However, the relapse rate in BAL patients was significantly higher than that of AML patients, while the CR rate after relapse was lower than that of AML patients. We also observed a low CR rate after relapse in BAL patients when compared with ALL patients, although no statistical difference was noted (p=0.083). Survival time and DFS after relapse in BAL patients were also shorter than those in AML or ALL patients. This may suggest that cross resistance more likely developed in BAL patients than in AML or ALL patients, causing a poor response to treatment and short survival period. Nakagawa et al.23 found that the overall expression levels of inhibitor of apoptosis protein (IAP)-family proteins in BAL bone marrow cells were higher than those in control, AML, and ALL cells. These results partly supported our observations.
Overall, the DFS and OS in our study were five and ten months, respectively. These were much shorter than those of AML and ALL patients in the same period (p<0.05). The OS and DFS of BAL patients were also less than eight months in other reports (Table 6). This might be due to: (i) common abnormal karyotype in BAL, high incidence of Ph chromosome, complex abnormal karyotype, and high incidence of abnormal chromosomes 5 and 7; (ii) high incidence of CD34 positive in BAL; (iii) high incidence of extramedullary infiltration; (iv) lack of optimized guidelines for induction therapy; and (v) high incidence of relapse after CR and resistance to therapy after relapse. Ottmann et al.24 reported that imatinib can improve CR rates in patients with refractory and relapse Ph positive ALL. For BAL patients with Ph chromosomes, imatinib added in treatment regimens might increase remission rates.
In summary, BAL is a particular kind of AL because of its rare incidence, difficulties in proper diagnosis and rational treatment. Thus, it is necessary to carry out multi-center co-operative studies in both clinical and basic research to further characterize the features of BAL.
JMW was the principal investigator and takes primary responsibility for the paper. XQX and JMW designed the study. XQX, SQL, LC, JMY, WPZ, XMS, JH, and XN recruited the patients. HYQ performed the laboratory work for this study. XQX and JMW wrote the paper. The authors reported no potential conflicts of interest.
Funding: this work was supported by grants from Science and Technology Commission of Shanghai Municipality (8JC1406500 and 5DZ19327) and from Ministry of Public Health, P.R China (KJ2007-3-001) to JMW.
Received for publication November 7, 2008. Revision received February 17, 2009. Accepted for publication February 19, 2009.
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