Paucity of TEL-AML 1 translocation, by multiplex RT-PCR, in B-lineage acute lymphoblastic leukemia (ALL) in Indian patients

Cytogenetics and Molecular Genetics in Pediatric Acute Lymphoblastic Leukemia (ALL) and Its Correlation with Induction Outcomes

Arathi SrinivasanAims  The aim was to study cytogenetics and molecular genetic profile in pediatric B-acute lymphoblastic leukemia (ALL) and correlate it with induction outcomes. Subjects and Methods  A retrospective study of cytogenetics and molecular genetics of 98 children with B-cell ALL from January 2013 to May 2018 was done. Cytogenetics and molecular genetics were done in the bone marrow using multiplex reverse transcription polymerase chain reaction and G-banded karyotyping, respectively. Minimal residual disease (MRD) assessment was done at the end of induction by flowcytometry. Results  Of the 98 children, 83 (84.6%) had evaluable cytogenetics, with 11 (13.25%) being abnormal karyotypes. Of the 11 abnormal karyotypes, seven children (8.4%) had hyperdiploidy, one had hypodiploidy, and three had miscellaneous findings. In molecular genetics, TEL-AML1 (ETV6/RUNX1)[t(12;21)] was the most common fusion gene abnormality (12.2% [12/98]), followed by E2A-PBX1 [t(1;19)] (5%), BCR/ABL1 [t(9;22)] (3%), and MLL-AF4 [t(4;11)] (1%). All the 98 children attained morphologic remission at the end of induction. All children with hyperdiploidy (7/7) attained remission and MRD negativity, but one expired during maintenance chemotherapy of disseminated tuberculosis. The child with hypodiploidy was MRD-positive. Three (25%) children with t (12;21) were MRD-positive. All children with Ph + ALL, t(1:19), and t(4;11) were MRD-negative. Fifty-two children had no detected abnormalities, six of whom had MRD positivity (11.5%). Conclusion  Cytogenetic and molecular genetic subgrouping prognosticates ALL outcomes. Although 25% of TEL-AML + children had MRD positivity, larger studies are required to validate the same. End-of-induction MRD outcomes did not correlate with chromosomal aberrations.

Retrospective Study of B Lymphoblastic Leukemia to Assess the Prevalence of TEL/AML1 in South India: A Study of 214 Cases and Review of Literature

Introduction Translocation t(12;21)(p13;q22), a recurrent and an invisible chromosomal abnormality, resulting in TEL/AML1 gene fusion, associated with good prognosis, has been described to be a common abnormality, in children with B-acute lymphoblastic leukemia (B-ALL).

Objectives The initial observation of very few TEL/AML1 positive patients at this center on testing by fluorescence in situ hybridization (FISH) led to study the prevalence of the abnormality, compare with the global distribution, and evaluate clinical, pathological, molecular, and cytogenetic features in TEL/AML1 positive patients.

Materials and Methods A retrospective study of all B-ALL patients tested for TEL/AML1 gene fusion during the period January 2009 to November 2020 was undertaken. Clinicopathological, molecular, cytogenetic, treatment, and follow-up details were collected. All publications dealing with TEL/AML1 gene rearrangement were reviewed post Google and PubMed search.

Results TEL/AML1gene rearrangement was assessed by FISH in 178 patients and by reverse transcription polymerase chain reaction in 36 patients and detected as the sole abnormality in 8.4% patients with additional genetic abnormalities noted on FISH evaluation. Normal karyotype was noted in 14/18 (77.7%) of these patients and 2 had complex karyotype. Complete blood count revealed hemoglobin to range from 35 to 116 g/L (median: 74 g/L), white blood count: 1.01–110×109/L (median: 7.8×109/L), platelet counts: 10–115×109/L (median: 42×109/L), blast count in peripheral smear: 0–98% (median: 41%). Immunophenotyping demonstrated 94.4% were CD34 positive, common acute lymphoblastic leukemia associated antigen (CALLA) positive with aberrant expression of CD13, CD33, CD56, singly or in combination in 58.8%.

Conclusion TEL/AML1 fusion is rare in Indian patients with B-ALL and appears to be much rarer in our region. The detection of relevant specific abnormalities is of fundamental importance in B-ALL patients and these geographic variations can be used in defining management policies.

Systematic Review of the Burden and Treatment Patterns of Adult and Adolescent Acute Lymphoblastic Leukemia in India: Comprehending the Challenges in an Emerging Economy

BACKGROUND

In the present systematic literature review, we sought to describe the burden and treatment practices of adult acute lymphoblastic leukemia (ALL) in India, which reflect the realities and outcomes in a middle-income country.

MATERIALS AND METHODS

We conducted a search for reported studies using terms such as "adult ALL," "epidemiology," and "treatment" in the Medline, Embase, Cochrane, and other database sources. We obtained 249 articles and 18 conference abstracts reported until December 2019. A total of 40 studies were selected to qualitatively summarize the data.

RESULTS

The proportion of ALL among adult patients diagnosed with acute leukemia at reporting institutions from 16 Indian studies ranged from 7.3% to 57.8%. Most studies were performed in Northern India (n = 12), had a male preponderance (range, 57%-80%), and had a predominance of B-ALL (range, 65.2%-75.9%). The treatment protocols used for ALL included MCP-841, BFM (Berlin-Frankfurt-Münster)-90, chemotherapy plus a tyrosine kinase inhibitor, GMALL (German Multicenter Study Group for Adult Acute Lymphoblastic Leukemia), and hyper-CVAD (cyclophosphamide, vincristine, doxorubicin, dexamethasone). The complete remission rates and median overall survival for these protocols ranged from 46.7% to 91.4% and 7 to 46 months, respectively. The overall relapse rates were 24.3% to 57.1% within median time of 9 to 24 months, with bone marrow the most frequent relapse site. After relapse, most patients had chosen palliative therapy (range, 78.7%-96.0%). The major treatment-related toxicities included neutropenia, myelosuppression, and infection.

CONCLUSIONS

The results from Indian studies on adult ALL are heterogeneous, reporting a diverse incidence and poor overall outcomes using varied non-contemporaneous treatment protocols adapted from the developed world. A comprehensive countrywide approach to diagnosis, treatment, and follow-up and the potential incorporation of novel therapies could improve the prognosis and outcomes of adult ALL in India.

Study of Cytogenetic Alterations and Association With Prognostic Factors in Indian Children With B-Lineage Acute Lymphoblastic Leukemia

BACKGROUND

Acute lymphoblastic leukemia (ALL) is a heterogeneous disorder with coexistence of multiple clones. The mortality rate in children with ALL has reduced to 15% to 20% in developed countries. However, it continues to be high in India (25%-35%), which may be attributed to ethnic variation and differences in disease biology. The treatment and outcome in ALL are dependent on risk stratification, which is derived from prognostic factors like leukocyte count, age at diagnosis, immunophenotypic subtypes and, most importantly, cytogenetic alterations. Chromosomal rearrangements are important initiating events in leukemogenesis. Approximately, 75% of children with ALL harbor a recurring chromosomal alteration detectable by karyotyping, fluorescence in situ hybridization, or other molecular techniques. The present study was planned to compare the prevalence of various cytogenetic alterations with western. literature and to see the association of these cytogenetic alterations with other prognostic factors as well as survival outcome.

METHODS

We enrolled, 117 children of 1 to 14 years of age with newly diagnosed B-cell ALL from August 2014 to Mar 2016 prospectively. Patients were monitored for response to prednisolone, postinduction complete morphological remission minimal residual disease assessment, and were followed for a minimum 2 years.

RESULTS AND DISCUSSION

We observed that poor-risk cytogenetic alterations were more prevalent, whereas good-risk cytogenetic alterations were less frequent in our patient cohort as compared with western studies.

CONCLUSIONS

We observed that event-free survival is significantly less in those with poor-risk cytogenetics. We have also highlighted nonrecurrent alterations observed in our study group.

Molecular profiling of gene copy number abnormalities in key regulatory genes in high-risk B-lineage acute lymphoblastic leukemia: frequency and their association with clinicopathological findings in Indian patients

Genes related to key cellular pathways are frequently altered in B cell ALL and are associated with poor survival especially in high-risk (HR) subgroups. We examined gene copy number abnormalities (CNA) in 101 Indian HR B cell ALL patients and their correlation with clinicopathological features by multiplex ligation-dependent probe amplification. Overall, CNA were detected in 59 (59%) cases, with 26, 10 and 23% of cases harboring 1, 2 or +3 CNA. CNA were more prevalent in BCR-ABL1 (60%), pediatric (64%) and high WCC (WBC count) (63%) patients. Frequent genes deletions included CDNK2A/B (26%), IKZF1 (25%), PAX5 (14%), JAK2 (7%), BTG1 (6%), RB1 (5%), EBF1 (4%), ETV6 (4%), while PAR1 region genes were predominantly duplicated (20%). EBF1 deletions selectively associated with adults, IKZF1 deletions occurred frequently in high WCC and BCR-ABL1 cases, while PAR1 region gains significantly associated with MLL-AF4 cases. IKZF1 haploinsufficiency group was predominant, especially in adults (65%), high WCC (60%) patients and BCR-ABL1-negative (78%) patients. Most cases harbored multiple concurrent CNA, with IKZF1 concomitantly occurring with CDNK2A/B, PAX5 and BTG1, while JAK2 occurred with CDNK2A/B and PAX5. Mutually exclusive CNA included ETV6 and IKZF1/RB1, and EBF1 and JAK2. Our results corroborate with global reports, aggregating molecular markers in Indian HR B-ALL cases. Integration of CNA data from rapid methods like MLPA, onto background of existing gold-standard methods detecting significant chromosomal abnormalities, provides a comprehensive genetic profile in B-ALL.

Gene copy number alteration profile and its clinical correlation in B-cell acute lymphoblastic leukemia

The genes related to B-cell development are frequently altered in B-cell acute lymphoblastic leukemia (B-ALL). One hundred sixty-two newly diagnosed B-ALL cases, median age 8.5 years (2 months-67 years), were prospectively analyzed for copy number alterations (CNAs) in CDKN2A/B, IKZF1, PAX5, RB1, ETV6, BTG1, EBF1, and pseudoautosomal region genes (CRLF2, CSF2RA, IL3RA) using multiplex ligation-dependent probe amplification. The CNAs were detected in 114 (70.4%) cases; most commonly affected genes being CDKN2A/B-55 (34%), PAX5-51 (31.5%), and IKZF1-43 (26.5%). IKZF1 and RB1 deletions correlated with higher induction failure. Patients classified as good-risk, according to the integrated CNA profile and cytogenetic criteria, had lower induction failure [5 (8.6%) vs. 20 (25.3%); p = 0.012]. Those classified as good-risk, based on CNA profile irrespective of cytogenetics, also showed lower induction failure [6 (9.4%) vs. 19 (26%); p = 0.012]. The CNA profile identified patients with better induction outcome and has a potential role in better risk stratification of B-ALL.

Cytogenetic Profile of De Novo B lineage Acute Lymphoblastic Leukemia: Determination of Frequency, Distribution Pattern and Identification of Rare and Novel Chromosomal Aberrations in Indian Patients

BACKGROUND

Chromosomal aberrations identified in acute lymphoblastic leukemia (ALL) have an important role in disease diagnosis, prognosis and management. Information on karyotype and associated clinical parameters are essential to physicians for planning cancer control interventions in different geographical regions.

MATERIALS AND METHODS

In this study, we present the overall frequency and distribution patterns of chromosomal aberrations in both children and adult de novo B lineage ALL Indian patients using conventional cytogenetics, interphase FISH and multiplex RT-PCR.

RESULTS

Among the 215 subjects, cytogenetic results were achieved in 172 (80%) patients; normal karyotype represented 37.2% and abnormal 62.8% with a distribution as follows: 15.3% hypodiploidy; 10.3% hyperdiploidy; 15.8% t(9;22); 9.8% t(1;19); 3.7% t(12;21); 2.8% t(4;11); 2.8% complex karyotypes. Apart from these, we observed several novel, rare and common chromosomal rearrangements. Also, FISH studies using LSI extra-signal dual-color probes revealed additional structural or numerical changes.

CONCLUSIONS

These results demonstrate cytogenetic heterogeneity of ALL and confirm that the incidence of chromosomal abnormalities varies considerably. To the best of our knowledge, this is one of the largest reported series of cytogenetic investigations in Indian B-lineage ALL cases. In addition, ongoing cytogenetic studies are warranted in larger groups of B-lineage ALL cases to identify newly acquired chromosomal abnormalities that may contribute to disease diagnosis and management.

Prevalence of common fusion transcripts in acute lymphoblastic leukemia: A report of 304 cases

AIM

Information about fusion transcripts in acute lymphoblastic leukemia (ALL) is used to risk-stratify patients, decide on the treatment and to detect minimal residual disease. This study was conducted to determine the frequency of common fusion transcripts BCR-ABL, TEL-AML1, MLL-AF4 and E2A-PBX1 for B-ALL and SIL-TAL1 for T-ALL as seen at a tertiary care center in India.

METHODS

Up to 304 new cases of ALL (271 B-ALL and 33 T-ALL) diagnosed on morphology, cytochemistry and immunophenotyping were studied. All were screened for the common fusion transcripts by RT-PCR.

RESULTS

Both our B- (218/271; 80.4%) and T-ALL (26/33; 78.8%) patients were largely children. In the B-ALL children, BCR-ABL was detected in 26/218 (11.9%), E2A-PBX1 in 13/218 (5.9%), TEL-AML1 in 16/218 (7.3%) and MLL-AF4 in 3/218 (1.4%) patients. Adult B-ALL cases had BCR-ABL in 15/53 (28.3%) and E2A-PBX in 2/53 (3.8%); however, no other fusion transcript was detected. SIL-TAL1 was found in four of 26 pediatric (15%) and zero of 7 adult T-ALL cases.

CONCLUSION

The higher incidence of BCR-ABL and lower incidence of TEL-AML1 in our ALL patients, both in children and adults as compared with the West, suggests that patients in India may be biologically different. This difference may explain at least in part the higher relapse rate and poorer outcome in our B-ALL cases.

Pattern of chromosome involvement in childhood hyperdiploid pre-B-cell acute lymhoblastic leukemia cases from India

BACKGROUND:

Hyperdiploid pre-B-cell acute lymhoblastic leukemia (pre-B-ALL) is a common form of childhood leukemia with very good prognosis with present day chemotherapy. However, the chromosomal composition of the hyperdiploidy has not been extensively studied and possible mechanism for this pathology remains so far conjectural.

OBJECTIVE:

To analyze the pattern of chromosome involvement in a cohort of childhood hyperdiploid pre-B-ALL from India and from this pattern to develop an understanding on the causation of such pathology. Whether such patients also carry translocations and FLT3 mutations in addition to their hyperdiploid karyotype.

MATERIALS AND METHODS:

One hundred and twenty-six childhood pre-B-ALL patients were studied. Bone marrow aspirate of these patients were evacuated for morphology, FAB classification, immunophenotyping and both conventional and molecular cytogenetics.

RESULTS:

Of 126 patients with pre-B-ALL (age 2-15 years), 90 patients with abnormal karyotype showed 50 with hyperdiploid karyotype (50/90 i.e. 55.5%). Chromosomes 9, 10, 14, 17, 18, 20 and 21 were more often involved in hyperdiploidy. Chromosome 21 duplication was present in 92% of the cases. Chromosomes 5, 15, 16, 17 and Y were less often involved (18-20%) in hyperdiploidy. About 44% of patients with hyperdiploidy had additional karyotypic abnormality of which TEL-AML1 was predominant (24%). Chromosome loss was rare and accounted for 20% of the cases only. We did not find any FLT3 mutation in our patients.

CONCLUSION:

In this study, the pattern of chromosome involvement in hyperdiploid karyotype of ALL patients is same as other studies except some chromosomes like 1, 6, 11, 12, 19 and 22 have some more frequent involvement than other studies. This study also showed the occurrence of TEL/AML1 fusion is more (19.8%) than other reports from India.

Utility of a multiplex reverse transcriptase-polymerase chain reaction assay (HemaVision) in the evaluation of genetic abnormalities in Korean children with acute leukemia: a single institution study

Purpose

In children with acute leukemia, bone marrow genetic abnormalities (GA) have prognostic significance, and may be the basis for minimal residual disease monitoring. Since April 2007, we have used a multiplex reverse transcriptase-polymerase chain reaction tool (HemaVision) to detect of GA.

Methods

In this study, we reviewed the results of HemaVision screening in 270 children with acute leukemia, newly diagnosed at The Catholic University of Korea from April 2007 to December 2011, and compared the results with those of fluorescence in situ hybridization (FISH), and G-band karyotyping.

Results

Among the 270 children (153 males, 117 females), 187 acute lymphoblastic leukemia and 74 acute myeloid leukemia patients were identified. Overall, GA was detected in 230 patients (85.2%). HemaVision, FISH, and G-band karyotyping identified GA in 125 (46.3%), 126 (46.7%), and 215 patients (79.6%), respectively. TEL-AML1 (20.9%, 39/187) and AML1-ETO (27%, 20/74) were the most common GA in ALL and AML, respectively. Overall sensitivity of HemaVision was 98.4%, with false-negative results in 2 instances: 1 each for TEL-AML1 and MLL-AF4. An aggregate of diseasesspecific FISH showed 100% sensitivity in detection of GA covered by HemaVision for actual probes utilized. G-band karyotype revealed GA other than those covered by HemaVison screening in 133 patients (49.3%). Except for hyperdiplody and hypodiploidy, recurrent GA as defined by the World Health Organizationthat were not screened by HemaVision, were absent in the karyotype.

Conclusion

HemaVision, supported by an aggregate of FISH tests for important translocations, may allow for accurate diagnosis of GA in Korean children with acute leukemia.

Pattern of relapse in childhood ALL: challenges and lessons from a uniform treatment protocol

This retrospective analysis of 254 children less than 15 years of age treated with MCP-841 protocol from June 1992 to June 2002 was undertaken to identify the pattern of relapse and determine management lacunae. Two hundred twenty-three (87.8%) children achieved a complete remission of whom 40 (17.9%) relapsed. The mean age of relapsed patients was 6.5 years. The male/female ratio was 9:1. There were 23 (57.5%) isolated bone marrow (BM), 7 (17.5%) isolated central nervous system (CNS), 2 (5%) isolated testicular, 5 (12.5%) BM+testes and 1 each of BM+CNS, CNS+testes, and isolated bone relapses. Twenty-seven children (67.5%) relapsed on-therapy whereas 13 (32.5%) relapsed posttherapy. All 9 CNS relapses occurred on-therapy whereas 5/8 (62.5%) of testicular relapses occurred posttherapy. Lymphadenopathy was the only significant predictor for relapse. High-risk features such as age less than 1 year and greater than 10 years (P=0.047) and white cell count greater than 50.0 x 10(9)/L (P=0.044) were significantly more frequent in patients with early on-therapy relapse than in patients with off-therapy relapse. The overall survival in the entire study cohort was 67+/-3.5%. Modest survival outcome, relapse while on chemotherapy and the higher incidence of CNS and testicular relapse indicate the need for reappraisal of our treatment protocol. There is a need of identifying risk factors and high-risk groups in our set of patients and risk-stratified intensification of chemotherapy in them.

Genetic rearrangement MLL/AF4 is most frequent in children with acute lymphoblastic leukemias in Mexico City

One of the highest incidences of acute lymphoblastic leukemia (ALL) in the world has been reported in Mexico City. In the current study (26 cases), the frequencies of the most frequent genetic rearrangements TEL-AML1, MLL/AF4, BCR-ABL (major and minor) in ALL in children from Mexico City were determined. For the ALL, the frequency of MLL/AF4 was 65.4%, for TEL-AML1 and that of BCR/ABL was 3.8%. Only 6 of the 17 children with the MLL/AF4 rearrangement were less than 26 months old. The frequency reported for MLL/AF4 in Mexican children with ALL is one of the highest worldwide. These findings could potentially explain the higher frequency of ALL with poor prognosis for children in Mexico City.

Detection and clinical relevance of BCR-ABL fusion gene in childhood T-lineage acute lymphoblastic leukemia: a report on 4 cases

The bcr-abl rearrangement has rarely been reported in T-lineage acute lymphoblastic leukemia and the clinical significance of this translocation is currently unknown. We screened 28 children with T-lineage acute lymphoblastic leukemia at diagnosis by reverse transcription polymerase chain reaction for major and minor break point regions of bcr-abl fusion gene. Four out of 28 patients (14.2%) were bcr-abl positive for the minor breakpoint transcript. One of these patients was refractory to therapy, whereas the other 3 relapsed on therapy.

Treatment of children with acute lymphoblastic leukemia in India using a BFM protocol

BACKGROUND

Limited data exists on the long-term treatment outcome and prognosis of childhood ALL in India.

PROCEDURE

Three hundred and seven children (1-14 years) with acute lymphoblastic leukemia (ALL) were treated with a modified BFM protocol 76/79 between 1985 and 2003. Treatment outcome and prognostic factors were evaluated.

RESULTS

The median age was 6 years; 78% had B lineage acute lymphoblastic leukemia and 22% had T lineage disease. Good prednisolone response was observed in 82% of cases. Two hundred and seventy-three children (91.6%) achieved complete remission; with 2% induction-related mortality and 6.4% having resistant disease. 52% of all evaluable patients and 56.8% of complete responders are in continuous complete remission (CCR) at a median follow up of 62 months (30-194 months). The median event free survival (EFS) was 114 months. The estimated 5 year overall survival, EFS and disease free survival was 59.8%, 56%, and 53.9%, respectively. The prognostic factors adversely affecting the EFS were poor prednisolone response, resistant disease and WBC count greater than 20 x 10(9)/L at diagnosis. The 5 year EFS in the favorable risk group (age 1-9 years, WBC count less than 20 x 10(9)/L and prednisolone good response) was 73.1 +/- 4.9%.

CONCLUSION

This report examines a cohort of children with ALL treated with a BFM protocol in India with adequate follow up and demonstrates the need for cost effective improvements.

Cytogenetics of Hispanic and White children with acute lymphoblastic leukemia in California

Epidemiologic studies of childhood leukemia have made limited use of tumor genetic characteristics, which may be related to disease etiology. We characterized the cytogenetics of 543 childhood leukemia patients (0-14 years of age) enrolled in the Northern California Childhood Leukemia Study, an approximately population-based study comprised primarily of Hispanics (42%) and non-Hispanic Whites (41%), and compared the cytogenetic profiles between these two ethnic groups. Subjects were classified by immunophenotype, conventional cytogenetic characteristics, and fluorescence in situ hybridization findings. The ploidy levels most frequently observed among acute lymphoblastic leukemia patients were high hyperdiploidy (51-67 chromosomes) and pseudodiploidy (34% and 27%, respectively). No ethnic differences in the frequency of 11q23/MLL rearrangements were observed between Hispanics and non-Hispanic Whites. Among B-lineage acute lymphoblastic leukemia patients, the percentage of TEL-AML1 translocations was significantly lower in Hispanics (13%) than in non-Hispanic Whites (24%; P = 0.01). This is the first time that this ethnic variation has been observed in a large number of patients in a defined geographic region, which is consistent with findings from smaller international studies. The mechanistic basis for this 2-fold variation in frequency of TEL-AML1 may be due to ethnic-specific risk factors or genetics and should be explored further.

Expression levels of TEL, AML1, and the fusion products TEL-AML1 and AML1-TEL versus drug sensitivity and clinical outcome in t(12;21)-positive pediatric acute lymphoblastic leukemia

PURPOSE

t(12;21)(p13; q22), present in approximately 25% of pediatric precursor B-ALL, is highly sensitivity to L-asparaginase and the prognosis depends on the intensity of the treatment protocol. This study analyzes the relationship between the mRNA expression of the genes and fusion products involved in t(12;21), in vitro sensitivity to prednisolone, vincristine, and L-asparaginase, and long-term clinical outcome in t(12;21)+ acute lymphoblastic leukemia (ALL) patients.

EXPERIMENTAL DESIGN

Long-term clinical outcome in 45 t(12;21)+ ALL patients was related to mRNA expression of TEL, AML1, TEL-AML1, and AML1-TEL, determined by real-time quantitative PCR, and the in vitro sensitivity to prednisolone, vincristine, and L-asparaginase, using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays.

RESULTS

A significant approximately 3.5-fold lower TEL expression in t(12;21)+ compared with t(12;21)- ALL samples (P = 0.006) and normal controls (P = 0.004) was found. Expression of AML1 did not differ between t(12;21)+ and t(12;21)- ALL. However, AML1 expression in the leukemic cells was 2-fold higher compared with normal controls (P = 0.02). The TEL-AML1 fusion product was expressed in all t(12;21)+ cases, whereas the reciprocal fusion product AML1-TEL was expressed in only 76%. High expression levels of TEL-AML1 [hazard ratio (HR), 1.3; 95% confidence interval (95% CI), 1.10-1.57; P = 0.003], AML1-TEL (HR, 4.9; 95% CI, 1.99-12.40; P = 0.001) and AML1 (HR, 1.1; 95% CI, 1.03-1.22; P = 0.006) were associated with a poor long-term clinical outcome within t(12;21)+ ALL. Cellular drug resistance towards prednisolone, vincristine, and L-asparaginase could not explain this predictive value. Multivariate analysis including age and WBC showed that only high AML1-TEL expression is an independent poor prognostic factor in t(12;21)+ childhood ALL.

CONCLUSION

High AML1-TEL expression is an independent poor prognostic factor in t(12;21)+ childhood ALL.