Consistent Chromosomal Changes in Chinese Patients with Acute Nonlymphocytic Leukemia

Although technical factors may affect the results of cytogenetic studies, a geo- graphic variation in occurrence of certain consistent chromosomal changes in acute nonlymphocytic leukemia (ANLL) has been reported [1-3]. The underlying reason may be ethnic or environmental factors. It would be interesting to see the chromo- somal patterns of Chinese patients with ANLL, especially when patients of different races have not been fully studied. Recently, we have successfully performed cyto- genetic studies in 32 unselected patients with ANLL. The patients were all Chinese, from Tianjin or other areas of northern China. Of the 32 patients, clonal chromo- somal abnormalities were found in 25 (78%), with several consistent chromosomal changes being revealed. Two patients showing abnormal eosinophils in the bone marrow were both found to have an inv(16)(p13q22) in the leukemic cells. Four patients with acute promyelocytic leukemia (APL) all showed t(15;17) or 17q- in poorly banded preparations. Two of the patients with acute monoblastic leukemia (M5a) had structural changes involving band 11q23. The most common abnormal- ity, t(8;21), was seen in six patients.

These six patients with t(8;21) made up 19% of our 32 cases of ANLL. This is similar to the frequency of t(8;21) in Japan and South Africa, which were 16% (6/37) and 13% (4/30), respectively, and much higher than that in western countries 6% (34/593) [2].

The incidence of leukemia in the western countries, including ANLL, rises sharply after the age of 50 years. This sharp rise in the incidence of leukemia is not present in China, where it does not change very much with the age of the popula- tion [4]. As a result, our patients are much younger than those from the west. The frequency of t(8;21), therefore, may be related to patient age. A further comparative study was performed between the present 32 patients and 82 previously published cases from Cambridge, England, on which data on patient age are available [8]. The patient age ranged from 0.5 to 85 years, with a mean of 52 years in the Cambridge series and from 5 to 82 years, with a mean of 31 years in the present series (p < 0.01). The frequency of t(8;21) was 4% (3/82) in the Cambridge series, and signifi- cantly lower than that (19%) in the present series of patients (p = 0.01). However, their age-adjusted frequencies are 6.3% and 8.9%, respectively (p - 0.25). This strongly suggests that patient age has contributed to the uneven geographic distri- bution of certain chromosomal abnormalities in leukemia.

According to the study by Swirsky et al. [5], a large number of patients with t(8;21) or related variants could not be classified as M2. In China we have diag- nosed subacute myelogenous leukemia (SML) since the late 1950s [6]. In this study, t(8;21) is specific for SML; i.e., all t(8;21) cases were SML and vice versa. Thus, the Chinese hematologists identified this group of patients by cytomorphology long be- fore cytogenetic studies were introduced. SML is not a widely accepted term, but

Received October 2, 1986; accepted October 14, 1986.

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380 Y-S. Li and C-L. Yang

some hematologists have not iced that not all t(8;21) cases meet the criteria for acute leukemia [5].

The FAB classification [7] has been wide ly accepted because of its under ly ing logic and relative ease of appl icat ion. However, none of the specific chromosomal changes comple te ly fits in the FAB classification except the t(15;17) and APL. In compar ison with FAB subtypes, patients with certain specific chromosomal changes appear to represent much more homogeneous groups for cl inical and re- search purposes. Thus, it is justified to reclassify leukemia in the light of cytoge- netic findings. The subtype of acute myelomonocyt ic leukemia with abnormal eo- s inophi ls (M4Eo) associated with the inv(16)(p13q22) or t ranslocat ions involving 16p13 and 16q22 appear to be examples of such attempts. SML or so-called t(8;21) leukemia might be another.

As expected, the chromosomal abnormal i t ies that have been related to pat ient age and exposure to potent ia l ly carcinogenic/mutagenic agents, such as + 8, 5 q - , 7 q - , - 5 , - 7 , are rare in China. In fact, there was not one pat ient who d isp layed 5 q - , 7 q - , - 5 or - 7 in the present study.

YOU-SHENG LI CONG-LI YANG

Institute of Hematology Chinese Academy of Medical Sciences

Tianjin, People's Republic of China

REFERENCES

1. Second International Workshop on Chromosomes in Leukemia (1980): Cancer Genet Cyto- genet 2:89-113.

2. Fourth International Workshop on Chromosomes in Leukemia, 1982 (1984): Cancer Genet Cytogenet 11:251-360.

3. Fitzgerald PH, Morris CM, Fraser GJ, Giles LM, Hamer JW, Heaton DC, Beard MEJ (1983): Nonrandom cytogenetic changes in New Zealand patients with acute myeloid leukemia. Cancer Genet Cytogenet 8:51-56.

4. Chou JL, Pan S-P (1985): Epidemiology of leukemias in the People's Republic of China. Leuk Res 9:777-780.

5. Swirsky DM, Li YS, Matthews JG, Flemans RJ, Rees JKH, Hayhoe FG] (1984): 8;21 translo- cation in acute granulocytic leukemia: cytological, cytochemical and clinical features. Br J Haematol 56:199-213.

6. Yang C-L, Yon W-W, Qi S-L, Yang T-Y, Wang Y-L (1982): Subacute myelogenous leukemia: A special type of myelogenous leukemia. Chinese Med J 95:459-466.

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8. Li YS, Khalid G, Hayhoe FGJ (1983): Correlation between chromosomal pattern, cytological subtypes, response to therapy, and survival in acute myeloid leukaemia. Scand J Haematol 30:265-277.