15;17 translocation in acute promyelocytic leukemia

15;17 Translocation in Acute Promyelocytic Leukemia David D. Hurd, Marjorie Vukelich, Diane C. Arthur, Leanna L. Lindquist, Robert W. McKenna, Bruce A. Peterson, and Clara D. Bloomfield

ABSTRACT: Acute promyelocytic leukemia (APL) is a relatively rare subtype of leukemia that has been reported to be associated with a specific chromosome abnormality, t(15;17). It has been suggested that this translocation may have a geographical distribution and its presence may signify a poorer prognosis. In this present series of 14 patients with APL, 9 patients (64%) had the t(15;17) and 5 did not; however, no significant differences in clinical features or outcome could be found between those who did and those who did not express the translocation. When ethnic backgrounds were explored, no differences were found. More cases of the t(15;17) were found in recent years (7 of 8 patients studied since 1978 compared to 2 of 6 before 1978). This corresponded to changes made in our cytogenetic techniques suggesting that the finding of the t(15;17) may be a function of technique, rather than a real difference in disease entities, and all patients with APL may have the t(15;17) when appropriately studied. INTRODUCTION Recent studies have found that approximately 40% of cases of acute promyelocytic leukemia (APL) demonstrate a 15;17 translocation [1-10]. It has been suggested that there may be a geographical distribution of patients with this translocation. The translocation has been reported to be present i n patients from Belgium, France, Japan, and the states of New York and Illinois, and absent in patients from F i n l a n d , Sweden, West Germany, Australia, England, Italy, and the state of Minnesota [7,9]. In addition, it has been suggested that this translocation is associated with a poorer prognosis [10]. We have studied bone marrow karyotypes from 14 patients with n e w l y diagnosed APL seen at the University of Minnesota Hospitals. In this paper we report the results of the chromosomal analyses and correlate these findings with ethnic background and clinical outcome.

From the Section of Medical Oncology, Department of Medicine, and the Department of Laboratory Medicine and Pathology, University of MinnesotaHealth Sciences Center, and the Masonic Cancer Center, Minneapolis. Address requests for reprints to Dr. David D. Hurd, Box 155, University of Minnesota Hospitals, Minneapolis, MN 55455. Received September 21, 1981; accepted November 9, 1981.

331 © Elsevier Science Publishing Co., Inc., 1982

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MATERIALS AND METHODS

In this retrospective study, the bone marrow cytogenetic material from all patients with newly diagnosed APL admitted to the University of Minnesota Health Sciences Center since 1973 was reviewed. Specimens for chromosome analysis were obtained from posterior iliac crest bone marrow aspirates. Since 1980 peripheral blood specimens from each newly diagnosed case of APL have also been studied in short-term, unstimulated, nonsynchronized culture, in addition to the bone marrow specimens. Of the 20 patients with APL seen, 14 had adequate chromosome studies. In the other 6 cases, mitoses were not obtained in 3 cases, the material was of a quality too poor for analysis in 2 cases, and the original slides were lost in 1 case. Samples were received and processed immediately after aspiration. Before 1978, the method of cell preparation used was a modification of the technique of Tjio and Whang-Peng [11]; since 1978, the technique of Hozier and Lindquist [12] has been used. Both methods involved direct harvest and a 24- or 48-hour unstimulated, nonsynchronized culture, provided that an adequate amount of material was available. All slides were stained first with a 1:50 Giemsa-phosphate buffer solution and scanned for suitable metaphases. Modal numbers were recorded, and nonbanded karyotype analyses performed. Whenever possible, metaphases from both the direct and cultured pellets were examined, but in some cases mitoses were obtained in only one of the pellets. When the quality of the material was suitable, slides were destained with a series of alcohols and restained with the Wright's G-banding technique of Sanchez et al. [13]. In some cases the material was quite poor and a complete G-banded analysis could not be done, but all cases were examined for the presence of t(15;17) as well as other gross chromosome abnormalities. Photographs were taken on Kodak high-contrast S0115 film using a green filter. Karyotyping was performed both under the microscope and with the use of the photokaryotypes. The diagnosis in all cases of APL was made based on the initial bone marrow aspiration and trephine biopsy by criteria previously described [14,15]. Cases were divided into typical APL and the microgranular variant of APL [14-17]. Clinical data were collected by reviewing all charts. Ethnic background information was obtained from patients and/or their families. Ten patients underwent induction chemotherapy with daunorubicin hydrochloride and a glucocorticoid [18]. Two patients received cytosine arabinoside in addition. The remaining two patients died rapidly before any treatment could be instituted. All patients had clinical and/or laboratory evidence of disseminated intravascular coagulation. Treatment of this consisted of the administration of continuous infusion heparin, platelet transfusions, and cryoprecipitate [18]. All patients obtaining complete remission (CR) were placed on maintenance therapy with 6-thioguanine and cytosine arabinoside [19]. Clinical features were compared in patients who had t(15;17) and those who did not. Differences between groups were evaluated for significance at the level of p -< 0.05. Differences in percentages for discrete variables were tested by the Pearson chi-square statistic test, correcting for continuity in 2 x 2 tables. Differences in continuous variables between groups were tested with the Mann-Whitney test. Differences in duration of remission and survival in the two groups of patients were evaluated using the Mantel-Haenzel 1-df chi-square test. The criteria for CR were patterned after those of the Cancer and Leukemia Group B [18]. In addition to requiring less than 5% myeloblasts and less than 10% myeloblasts plus promyelocytes in the marrow, the promyelocytes had to be morphologically normal and coagulation parameters had to be normal. Duration of remission

15;17 Translocation in APL Table 1

333

Cytogenetic findings in 14 patients w i t h APL Number of Mitoses

Case

Total

Normal Diploid

Abnormal Clonal

1 2°

12 10 b

9 4

3 6

3 °'c

13

10

3

4a

12

7

5

5 "'c 6c

20 30

12 0

8 30

7a

17

13

4

9 °'c

50 7b

50 0

0 3 4

10

5

5

0

19

19

0

12

6

6

0

13

20

20

0

14

12

0

12

11 a'c

Banded karyotypes of bone marrow clones 46,XY/46,XY,t(15; 17)(q24?;q21?) 46,XY/46,XY,t(15;17)(q24?;q21?) 46,XX/46,XX,t(15; 17)(q24?;q21?) 46,XY/46,XY,t(15;17)(q24?;q21?) 46,XY/46,XY,t(15; 17)(q24?;q21?) 46,XY,t(15;17)(q24?;q217) 46,XY/46,XY,t(15; 17)(q24?;q21?) 46,XY Clone 1: 46,XY,t(15;17)(q24?;q21?) Clone 2: 46,XY,t(15;17)(q24?;q21?), t(1;9)(p36;q22) 46,XX 46,XY 46,XX 46,XX 46,Xinv(Y)

aTechniques of Hozier and Lindquist [12], others by those of Tjio and Whang-Peng [11]. bPeripheral blood specimen. cStudies on both direct and cultured material.

was m e a s u r e d from the time CR was obtained to the first d o c u m e n t a t i o n of recurrent leukemia. Survival was calculated from the date of diagnosis. RESULTS Results of the cytogenetic analyses are s h o w n in Table 1. In 9 of 14 patients t(15;17) (Fig. 1) c o u l d be demonstrated. Eight of 9 patients had t(15;17) as the sole karyotypic abnormality. A l l but 1 of these 8 (case 6) h a d normal d i p l o i d cells present also. Fifty m a r r o w cells were e x a m i n e d in case 9, and all were normal; however, two abnormal clones were identified in p e r i p h e r a l b l o o d cells. Four patients h a d completely n o r m a l marrow karyotypes, and the r e m a i n i n g patient had another chrom o s o m a l abnormality. The clinical characteristics of patients who had t(15;17) and those w h o d i d not are s u m m a r i z e d in Table 2. No statistically significant differences were seen in this small group of patients. However, more males were seen in the translocation group (seven of nine c o m p a r e d to two of five). Similarly the m e d i a n age of the t(15;17) group was 36 years c o m p a r e d to 47 years for the group w i t h o u t the translocation; the age ranges were similar in both groups. The microgranular variant occurred in four of nine patients in the t(15;17) group, whereas it was seen in only one patient without the translocation. The m e d i a n leukocyte counts at diagnosis (5.0 × 109 and 2.0 × 10Yliter) were similar in the two groups, however, the range was greater in the t(15;17)group (1.0-130.0 x 109 versus 1.5-21.4 x 109/liter). Patients with t(15;17) less frequently achieved CR (five of eight versus four of four). One patient in each group was not treated because of their r a p i d demise. Patients in the group w i t h o u t the translocation had a m e d i a n d u r a t i o n of CR of 112 weeks c o m p a r e d to 24 weeks in the t(15;17) group. The m e d i a n length of survival for the group w i t h o u t the translocation was 72 weeks c o m p a r e d to 4 weeks in pa-

334

1

2

tl ,ii 4

3

5

ii 1,! il, iI i'i 6

7

8

13

14

15

19

20

9

10

\

11

12

X

16

17 y'

18

21

22

Y

F i g u r e 1 G-banded karyotype from bone marrow in case 8 at diagnosis showing 46,XX,t(15; 17)(q24?;q21?).

Table 2 Clinical characteristics of patients with and without t(15;17) Characteristic

With t(15;17)

Number of patients Number of males Age (yr) Median Range Microgranular variants Median initial leukocyte count (per liter) Number of patients achieving CR Median duration of CR (wk) Median survival (wk)

9 7

Without t(15;17) 5 2

36 26-71 4 5.0 × 109

47 31-61 1 2.5 X 1 0 9

5 24 ° 4°

4 112 72

°Two patients (cases 8 and 9) have just achieved CR and have been excluded from the analysis.

335

15;17 Translocation in APL Table 3

Ethnic background for patients w i t h and w i t h o u t t(15;17)

Family background

With t(15;17)

Without t(15;17)

Number of patients Born in United States Born outside United States Number of parents Born in United States Born outside United States Number of grandparents Born in United States Born outside United States Number of great-grandparents Born in United States Born outside United States

9 8 1° 18 10 8b 36 8c 28d 72 2c 70e

5 5 0 10 8 2f 20 4 16g 40 0 408

aSeychelleIslands. bSeychelleIslands, Germany, Ireland, Sweden, CAmericanIndian. dSeychelleIslands, Ireland, Sweden, Czechoslovakia,Germany, England. eSeychelle Islands, Ireland, Sweden, Czechoslovakia, Germany, England, France, Netherlands, Denmark, Poland. 1Czechoslovakia. gCzechoslovakia,Germany, Russia, Ireland.

tients with the translocation. Two patients in the t(15;17) group have just achieved CR and were e x c l u d e d from the analysis of duration of CR and survival. W h e n the ethnic backgrounds of the patients were investigated, differences bet w e e n the two groups were not detected (Table 3). Czechoslovakian, Irish, and German backgrounds were seen in both groups. Patients with the translocation had extremely diverse ethnic backgrounds i n c l u d i n g A m e r i c a n Indian and ancestors from Sweden, Denmark, England, France, Poland, The Netherlands, and the Seychelle Islands, as well as those m e n t i o n e d above. DISCUSSION In our current series of patients, w e have found an i n c i d e n c e of the t(15;17) in APL that was similar to but s o m e w h a t higher (64% versus 40%) than that reported b y the First and Second International W o r k s h o p s on Chromosomes in L e u k e m i a [9, 10]. The two patients from the state of Minnesota p r e v i o u s l y reported at the Second W o r k s h o p d i d not have the translocation. A l t h o u g h the majority of our patients were second-, third-, and fourth-generation Americans, we noted in their ancestral backgrounds, nationalities reported not to develop this particular translocation, that is, English, German, and S w e d i s h [7,10]. In our patients, we noted that more cases with t(15;17) were seen in recent years (seven of eight cases since 1978 c o m p a r e d to two of six cases before 1978). This observation might be e x p l a i n e d on the basis of the change in cytogenetic techniques, described above, initiated in 1978. Other authors have also p r o p o s e d that methodological factors p l a y a role in y i e l d i n g s p u r i o u s l y n o r m a l karyotypes, that is, the direct m e t h o d of marrow analysis showing d i p l o i d cells, but the c u l t u r e d preparations of 24 or more hours revealing the abnormal clone [20,21]. In our

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study, w h e n direct and cultured preparations were both e x a m i n e d (six patients), the results of both techniques were in agreement w h e t h e r n o r m a l or showing the translocation. If the cells of more of our patients had been s t u d i e d in culture, perhaps t(15;17) w o u l d have been found more frequently [20,21]. It is of course possible that other unidentified variables m a y have a role in this seemingly increased incidence of t(15;17) detected at our institution since 1978. The assignment of precise break points in t(15;17) has been difficult using Gb a n d e d material because of the similar appearance of the distal third of chromosome No. 15 and band 17q21 [10]. In two of our recent cases (patients 8 and 9) the c h r o m o s o m e material has been of particularly good quality. As s h o w n in Figure 1, the distal dark bands on chromosomes No. 15 and 17 stain with a slightly different intensity. From this material it appears that there has been a reciprocal exchange of the material distal to bands 15q24 and 17q21, and we have therefore assigned the break points (q24?;q21?). A similar assignment has been m a d e by Yunis et al. [22] in a recent report on two cases of APL studied with G-banding. With respect to clinical differences between patients who have t(15;17) and those who do not, our data are in agreement with those reported from the Second International Workshop on Chromosomes in Leukemia with regard to age, APL variants, CR rate, and survival. In both patient populations, t(15;17) was seen more often in younger patients and those w i t h microgranular forms of APL. Because APL is a relatively rare disorder, c o m p r i s i n g only 5% of acute n o n l y m p h o c y t i c leukemias, too few patients have been adequately s t u d i e d to make definitive statements as to w h e t h e r t(15;17) affects the clinical presentation or course of this disease. If all cases of APL actually have t(15;17) and its d e m o n s t r a t i o n is s i m p l y d e p e n d e n t u p o n a p p l i c a t i o n of the appropriate cytogenetic techniques, the differences in clinical features between cases with and without the translocation become p r i m a r i l y a function of the cytogenetic technique rather than the real presence or absence of the translocation. Our data suggest that there is no ethnic association with this translocation. This work was supported by Grant CA-19527 from the National Cancer Institute of the United States Public Health Service, the Masonic Hospital Fund, Inc., the Minnesota Medical Foundation, and the Coleman Leukemia Research Fund. The authors wish to thank Sharla Watermolen for technical assistance.

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