MJ Sutcliffe 1,2, JJ Shuster 3, HN Sather 4, BM Camitta 5, J Pullen 6, KR Schultz 7, MJ Borowitz 8, PS Gaynon 9, AJ Carroll 10 and NA Heerema 11

Transcription

1 (25) 19, & 25 Nature Publishing Group All rights reserved /5 $3. High concordance from independent studies by the Children s Cancer Group (CCG) and Pediatric Oncology Group (POG) associating favorable prognosis with combined trisomies 4, 1, and 17 in children with NCI Standard-Risk B-precursor Acute Lymphoblastic : a Children s Oncology Group (COG) initiative MJ Sutcliffe 1,2, JJ Shuster 3, HN Sather 4, BM Camitta 5, J Pullen 6, KR Schultz 7, MJ Borowitz 8, PS Gaynon 9, AJ Carroll 1 and NA Heerema 11 1 Department of Pathology, All Children s Hospital, St Petersburg, FL, USA; 2 Department of Pediatrics, University of South Florida, Tampa, FL, USA; 3 Children s Oncology Group Research Data Center, and Department of Statistics, University of Florida, Gainesville, FL, USA; 4 Department of Preventative Medicine, University of Southern California, Los Angeles, CA, USA; 5 MidWest Children s Cancer Center, Department of Pediatrics, Medical College of Wisconsin and Children s Hospital of Wisconsin, Milwaukee, WI, USA; 6 University of Mississippi Medical Center, Jackson, MS, USA; 7 British Columbia s Children s Hospital, University of British Columbia, Vancouver, BC, Canada; 8 Department of Pathology, John Hopkins University, Baltimore, MD, USA; 9 Department of Hematology-Oncology, Children s Hospital, Los Angeles, CA, USA; 1 Department of Genetics, University of Alabama at Birmingham, Birmingham, AL, USA; and 11 Department of Pathology, The Ohio State University, Columbus, OH, USA Chromosome aberrations have a major role in pediatric acute lymphoblastic leukemia (ALL) risk assignment. The Children s Cancer Group (CCG) and the Pediatric Oncology Group (POG) independently assessed the significance of trisomy for chromosomes 4, 1, and 17 in National Cancer Institute (NCI) Standard- and High-Risk ALL. Data from 1582 (CCG) and 392 (POG) patients were analyzed. Eight-year event-free survivals (EFS) of 91% (CCG) and 89% (POG) (Po.1) were achieved in patients assigned to NCI Standard Risk whose leukemic cells had simultaneous trisomies 4, 1, and 17. Both groups showed the degree of favorable prognostic importance increased with the actual number of favorable trisomies. POG analyses also demonstrated hyperdiploidy (X53 chromosomes) was less of an independently significant prognostic factor in the absence of these key trisomies. This finding supported conclusions from previous CCG and POG studies that specific trisomies are more important than chromosome number in predicting outcome in pediatric B-precursor ALL. In NCI Higher Risk patients, the number of favorable trisomies was not prognostically significant, but showed the same trend. Moreover, specific trisomies 4, 1, and 17 remain associated with favorable prognosis in Standard-Risk B-precursor ALL, even in the context of very different treatment approaches between the groups. (25) 19, doi:1.138/sj.leu Published online 24 March 25 Keywords: COG; CCG; POG; B-precursor acute lymphoblastic leukemia; cytogenetics; trisomy Introduction Traditionally, patient age and white blood cell (WBC) count at the time of presentation with acute lymphoblastic leukemia (ALL) have been used to stratify risk and assign variably intensive treatment protocols. 1,2 Although many other clinical and biological factors have been identified and assessed for prognostic value, 3 few remain significant when subjected to multivariate analysis. 4,5 One factor that consistently appeared favorable, even in the context of other risk factors, was chromosome number and further analyses suggested the Correspondence: MJ Sutcliffe, c/o Donna Correia, Publications Coordinator, Children s Oncology Group, PO Box 612, Arcadia, CA , USA; Fax: þ ; dcorreia@childrensoncologygroup.org Received 26 March 24; accepted 23 December 24; Published online 24 March 25 presence of specific chromosomes could be more important than a simple increase in ploidy. 6 8 The initial observation linking an increase in modal chromosome number with prognostic significance in childhood ALL was made in Verification of the association between hyperdiploidy and favorable prognosis has been the subject of numerous independent studies Initially, the most favorable prognosis was ascribed to the modal number of chromosomes comprising high hyperdiploidy, defined as chromosomes. Further refining indicated the most favorable outcome in the group with and subsequently chromosomes. 6 Although hyperdiploidy can involve any chromosome, the frequent non-random involvement of specific chromosomes is striking. 6 8,14,18,2 22 In a prior Pediatric Oncology Group (POG) study, using statistical recursive partitioning analysis, simultaneous trisomies of chromosomes 4 and 1 were found to be strongly indicative of favorable prognoses. 7 Moreover, POG demonstrated that ploidy (as measured by DNA index or o1.16) appeared to lose independent statistical prognosis in the absence of simultaneous trisomies of chromosomes 4 and 1. 7 More recently, the Children s Cancer Group (CCG) found less significance for trisomy 4 but significant prognostic value for trisomies 1, 17, and to a lesser extent Moorman et al 8 also cited trisomies 4 and 18 as independent positive indicators in the United Kingdom studies. Within their cohort of high hyperdiploid patients, the CCG found that trisomy for chromosome 1 was the strongest predictive component in both univariate and multivariate analyses. 6 The Children s Oncology Group (COG) was formed as a result of the merger of the CCG and the POG. A COG high priority is risk group classification to identify the lowest risk group of children with B-precursor ALL. Although good trisomies (GTs) were considered favorable prognostic factors for CCG and POG, they had been defined differently. 6,7 Variable combinations of the trisomies with patient outcome were examined using the independently derived CCG and POG data sets. Despite differences in treatment strategies between the CCG and POG protocols, the findings showed a striking concordance between the presence of combined trisomies of chromosomes 4, 1, and 17 and an excellent prognosis in Standard Risk B-precursor ALL. Moreover, when any of these key favorable trisomies were absent, a significant trend towards a worse prognosis was noted. The data are significant because, irrespective of the disparity between the two groups initial data collection design and

2 without pooling data, a high concordance in outcome was independently demonstrated in a very large number of patients. Consequently, the simultaneous presence of these trisomies appears to define a group of children with ALL who might benefit from less toxic therapeutic protocols. 23 Materials and methods Cytogenetic analysis and diagnostic criteria Inclusion or exclusion of particular karyotypic findings varied according to the different historical concepts and ideologies of the two groups protocols, detailed in Supplementary Appendix 1a. In general, both CCG and POG informative cytogenetics included an abnormal clone with structural or numerical abnormalities but excluded translocations (4;11) or (9;22), unsatisfactory cytogenetics and infants o1 year old. While normal karyotypes were acceptable by the CCG, data were collected but excluded from analysis by the POG. Diagnostic criteria are described in Supplementary Appendix 1b. Both the CCG and POG used cytochemical stains, morphology and immunophenotyping consistent with B precursor ALL; however, immunophenotyping was unavailable for a proportion of early protocol patients in the CCG protocols. Patients Ages 12 months to years with newly diagnosed B-precursor ALL consecutively enrolled on CCG and POG protocols. Of 5121 patients initially enrolled in the CCG protocols, final data for 1582 patients were included whereas POG included data from 392 from the 668 patients initially enrolled. For inclusion/exclusion patient enrollment details, see Supplementary Appendix 1c. Risk classification Both the CCG and POG assigned patients to preliminary risk groups for induction therapy according to the NCI uniform risk group definitions. 2 Standard Risk: Age o1 years, and WBC count o5 /ml; High Risk: Age X1 years, or WBC count X5 /ml. Statistical methods The primary outcome index used was EFS calculated as the time from entry onto the respective protocols to the first occurrence of any of the following events: induction failure, relapse at any site, secondary malignancy, or death. Patients without events were censored at the time of last contact. EFS curves were constructed by the Kaplan Meier life table procedure. Standard deviation of the Kaplan Meier estimates was based on the Peto variance estimates for the life table curves. 24 The groups used the log-rank test for statistical comparison. Treatment Prognosis with combined trisomies 4, 1, 17 in ALL Details of the CCG and POG treatment protocols for the different studies are summarized in Supplementary Appendix 1d. In general, the CCG studies utilized modification of the Berlin Frankfurt Munich (BFM) regimen with increased asparaginase utilization while the POG protocols were antimetabolite-based emphasizing intensification with intermediate-dose methotrexate (IDMTX). 25,26 Supplemental information on cytogenetic analysis, diagnosis, patients eligibility for inclusion in the final data sets and summary of treatment protocols of the two groups is available in Supplementary Appendices 1a d on the website. Results In early analyses, the POG 7 found that after adjusting for trisomies 4 and 1, no other trisomies were significantly prognostic, whereas the CCG 6 found that trisomies of 4, 1, 17, and 18 were independently prognostic. Both groups subsequently concluded that when all four trisomies were considered collectively, trisomy 18 added little prognostic information to that already obtained from the other three trisomies (data not shown); therefore, subsequent analyses focussed on chromosomes 4, 1, and 17. NCI risk categories Historically, the CCG and POG did not use the same risk group assignments. Since NCI risk grouping is internationally accepted as a standard method of comparing different group s data, NCI risk groups were used so that stratification between the CCG and POG would be identical. Furthermore, this has become the standard adopted for ongoing COG studies. Standard-risk CCG: Table 1 illustrates the 5- and 8-year EFS results arranged according to the presence or absence of the key GTs, chromosomes 4, 1, and 17, in hyperdiploid B-precursor ALL patients assigned to the NCI Standard Risk category. When patients had all three GTs, EFS was 91% at 5 years (SE 2.6) and 8 years (SE 4.2). With respect to patients with two GTs, apart from a small group with þ 1, þ 17 that showed excellent EFS, two GTs had 12 15% (5 years) and 15 17% (8 years) lower EFS, when compared with all three GTs. A few patients with only þ 17 had a good EFS, but lower EFS was noted for those with only one GT for trisomy 4 or 1. The absence of any of the GTs (no GTs) showed EFS reduced by 18% and 21% at 5 and 8 years, respecitively. EFS for patients with abnormal karyotypes and all three, two, one, or none of the favorable trisomies is significantly different (Po.1, Figure 1a). Standard-risk POG: EFS at 5 and 8 years for the NCI Standard Risk category are shown in Table 1. There was a statistically significant difference in outcome according to the number of GTs (four-way, Po.1; two vs three GTs, P ¼.9; one vs two GTs, Po.1) but not for zero vs one GT, P ¼.39. Regarding the specific trisomies present, 4 vs 1 vs 17, there were no significant differences (which GT within two GTs (three-way), P ¼.64 and which GTs within one GT (threeway), P ¼.76). Figure 1b summarizes the 5-year EFS data for all POG NCI Standard Risk patients with abnormal karyotypes as to outcome for patients with three, two, one or none of the favorable trisomies. High-risk CCG: EFS data for patients classified as NCI High Risk is shown in Table 2. No significant difference in EFS at a conventional significance criterion was observed according to the number of GTs. However, those with two or three GTs showed the same trend as the standard-risk group. One 735

3 736 Table 1 Prognosis with combined trisomies 4, 1, 17 in ALL CCG and POG data showing EFS at 5 and 8 years with respect to number of GTs in NCI Standard-Risk patients with ALL CCG ( ) and POG ( ): standard risk Chromosomes Children s Cancer Group Pediatric Oncology Group No of patients 5-year EFS (s.e.) 8-year EFS (s.e.) No of patients 5-Year EFS (s.e.) 8-Year EFS (s.e.) % % % % 4+, 1+, (2.6) 91.1 (4.2) (1.6) 89.2 (2.8) 4+, 1+, (7.6) 72.4 (1.2) (4.2) 82.5 (6.2) 4+, 1, (5.8) 76.3 (9.9) (3.7) 8.9 (6.7) 4, 1+, (4.3) 95.8 (6.9) (4.9) 87.3 (7.1) 4+, 1, (1.3) 68.8 (15.7) (6.7) 65.6 (12.2) 4, 1+, (7.2) 79.5 (14.7) (5.5) 73.7 (1.1) 4, 1, (7.3) 9.2 (11.5) (5.7) 74.9 (8.6) 4, 1, 17 a (2.7) 7.5 (5.) (1.8) 67.8 (2.9) Normal karyotype (2.1) 83.6 (3.8) 969 b 81. (1.7) 78.9 (2.5) Total patients Total in study a May include other numerical of structural abnormalities. b Not included in POG final data (see Methods) and Supplementary Appendix 1a. exception, specifically 4 and 1, showed the presence of two GTs associated with 9% EFS at 5 and 8 years, but this group comprised o2% of patients. Figure 2a summarizes the 5-year EFS data for CCG NCI High-Risk patients with abnormal karyotypes with three, two, one, or no favorable trisomies. High-risk POG: Data in Table 2 demonstrates a significant trend towards those with fewer GTs having worse prognoses (P ¼.1, four-way), but no statistically significant differences between any adjacent pair (three vs two GTs, P ¼.96; two vs. one GTs, P ¼.6; one vs zero GTs, P ¼.86). Within two GTs or one GT, there was no significant difference as to which chromosomes were trisomic (P ¼.46 and ¼.12). The 5-year EFS data for POG NCI High Risk patients with abnormal karyotypes is shown in Figure 2b. Modal number of chromosomes Previous analyses concluding that hyperdiploidy appeared to lose independent significance when compared to the significance of individual trisomies. 7 Hence, the current data were examined to determine whether modal number increased predictive outcome when compared to that of the three GTs. Based on X53 chromosomes being considered the most prognostic 6 and the DNA index of 1.16 (used since 1986), the cutoff was established. For NCI Standard-Risk patients, univariate analysis of p52 vs X53 chromosomes was prognostic in both groups. Standard risk: Table 3 shows the modal number of chromosomes and number of trisomies for the POG NCI Standard-Risk group. After stratifying for chromosome count p52 vs X53, the number of GTs remained statistically significant (P ¼.5) with respect to prognosis. Conversely, chromosome count p52 vs X53 was found not to be statistically significant (P ¼.44). The results of CCG analysis using the same split were comparable (data not shown) but there were insufficient data for statistical analysis. High risk: The POG data regarding the relationship of modal number and the number of GTs for the NCI High-Risk group is also shown in Table 3. After stratifying for modal number p52 vs X53, or for the number of GTs, neither were prognostically significant (P ¼.79 and.76, respectively). The CCG data had a similar outcome but were insufficient within each category for statistical analysis (data not shown). Discussion The data in this paper, relevant to about 25% of children with B-precursor acute lymphoblastic leukemia, indicate that children with NCI Standard-Risk B-precursor ALL have long-term EFS of 9% if their leukemic cells have simultaneous trisomies of chromosomes 4, 1, and 17. These results were observed in both the CCG and POG studies despite the differences in data collection strategies and treatment protocols used by the two groups. 25,26 A number of previous studies have indicated that hyperdiploidy was the strongest predictor of treatment outcome 8,1,16 within standard-risk ALL. In the same cohort studied by Trueworthy et al 15 results of Harris et al 7 analyses challenged this traditionally held notion by demonstrating that good outcome could be explained by specific trisomies of 4 and 1 alone. This concept does not imply hyperdiploidy is of no value but indicates that more specific factors, over and above chromosome count, might provide better prognostic information. Consequently, in 1994, POG discontinued high hyperdiploidy in favor of specific trisomies in patient treatment assignment. Heerema et al 6 reported trisomy for chromosomes 1 and 17 conferred a good prognosis but restricted their analysis to specific trisomies within different hyperdiploid subgroups. Nonetheless, this strategy does not preclude analyses without ploidy subgrouping. Of course, it is rare for patients with three or two GTs not to also be in the high hyperdiploid subgroup, as demonstrated by the NCI Standard-Risk POG data shown in Table 3. But even these few patients (4/746 with three GTs and 21/463 with two GTs) demonstrated a 1% and 88% EFS, respectively. It is accepted that the small number of discordant patients between the group of hyperdiploid patients and those with favorable trisomies makes it difficult to exclude

4 Prognosis with combined trisomies 4, 1, 17 in ALL a 1 Number of Good Trisomies 4, 1, CCG 18s/1922 Series NCI Standard Risk Two (n=125) Three (n=15) One (n=92) None (n=332) 4 b Yr Three Two One None POG ALinC 14, 15, 16 NCI Standard Risk Number of Good Trisomies 4,1,17 Number 5 Yr Three Two One None Three (n=746) Two (n=465) One (n=35) None (n=121) Figure 1 (a) Number of GTs relationship to EFS for (a) CCG protocols 18s/1922 Series B-precursor ALL NCI Standard-Risk patients and (b) POG protocols ALinC 14, 15, 16 Series B-precursor ALL NCI Standard-Risk patients. the possibility of ploidy still being important in some specific subgroups of patients with trisomies. However, overall our current findings do not contradict, and appear to extend, the observations of Harris et al 7 as relates to Standard-Risk B-precursor ALL pediatric patients. More specifically, it is not simply hyperdiploidy, but trisomy for the specific chromosomes 4, 1, and 17, that is the strongest predictor of treatment outcome. As a consequence of our findings, FISH strategies involving specific trisomies, irrespective of ploidy, are planned in future COG risk assessment. Trisomies 4, 1, and 17 were associated with a better outcome in the NCI Higher-Risk category, but results were clinically unimportant in determining a good prognostic subset of patients. Although perhaps appearing at odds with the excellent correlative findings in standard-risk patients, this observation is not necessarily surprising. Standard- and high-risk patients are known to fare unequally irrespective of any biological characteristics so far described and it appears that trisomy is not an exception. The etiology of increased chromosome number remains unclear, but it is evident that only certain chromosomes are consistently present in excess in high hyperdiploid karyotypes in ALL. 6 8,19,21 Although any of the 24 chromosomes may be present in increased copy number only ten (chromosomes 4, 5, 6, 8, 1, 14, 17, 18, 21, and X) are nonrandomly associated with high hyperdiploid karyotypes in ALL and only eight are consistently present in over 5% of these patients. Increased

5 738 Table 2 Prognosis with combined trisomies 4, 1, 17 in ALL CCG and POG data showing EFS at 5 and 8 years with respect to number of GTs in NCI High-Risk patients with ALL CCG ( ) and POG ( ): high risk Chromosomes Children s Cancer Group Pediatric Oncology Group No. of patients 5-year EFS (s.e.) 8-year EFS (s.e.) No of patients 5-year EFS (s.e.) 8-year EFS (s.e.) % % % % 4+, 1+, (7.9) 79.3 (13.6) (5.8) 69.8 (9.) 4+, 1+, (1.8) 9. (28.5) (12.1) 64.3 (15.7) 4+, 1, (13.6) 67.1 (38.5) (12.2) 65.9 (22.2) 4, 1+, (19.1) 71.4 (38.2) (17.4) 82. (2.1) 4+, 1, (21.9) NA (12.2) 6.1 (26.8) 4, 1+, (12.8) 56.2 (37.2) (11.1) 58. (18.8) 4, 1, (16.6) NA (F) 1. (F) 4, 1, 17 a (3.1) 67.8 (5.4) (2.6) 54.8 (4.2) Normal karyotype (4.2) 74.1 (8.7) 384 b 62.1 (3.4) 59.9 (5.9) Total patients Total in study a May include other numerical of structural abnormalities. b Not included in POG final data (see Methods) and Supplementary Appendix 1a. a 1 9 Number of Good Trisomies 4, 1, Three (n=34) Two (n=3) None (n=284) Probability b CCG 18s/1922 Series NCI High Risk 5 Yr Three Two One None Number of Good Trisomies (4,1,17) One (n=36) Three (n=127) Two (n=92) One (n=86) Probability POG ALinC 14, 15, 16 NCI High Risk Number 5 Yr Three Two One None None (n=835) Figure 2 (a) Number of GTs relationship to EFS for (a) CCG protocols 18s/1922 Series B-precursor ALL NCI High-Risk patients and (b) POG protocols ALinC 14, 15, 16 Series B-precursor ALL NCI High-Risk patients.

6 Table 3 Prognosis with combined trisomies 4, 1, 17 in ALL EFS for POG NCI Standard- and High-Risk patients according to modal chromosome number and number of GTs 739 No of GTs Hyperdiploid count Standard risk High risk No 5-year EFS (s.e.) 8-year EFS (s.e.) No 5-year EFS (s.e.) 8-year EFS (s.e.) chrms (1.6) 89.1 (2.8) (5.8) 69.8 (9.) o53 chrms 4 1. (F) 1. (F) 1 F F chrms (2.5) 82.9 (4.) (8.4) 66.6 (11.6) o53 chrms (12.5) 87.8 (13.7) (21.2) 77.8 (36.7) chrms (4.6) 75.3 (8.) (9.3) 76.4 (14.) o53 chrms (5.) 68.6 (8.4) (11.6) 52.1 (25.6) 452 chrms (1.7) 8.6 (13.4) (16.) 51.3 (25.3) o53 chrms (1.8) 67.5 (2.9) (2.6) 54.8 (4.2) Total Note: Cutoff 53 chromosomes. copy number of chromosome 21, with a relative frequency of almost 95%, and chromosome X, with a relative frequency of approximately 85%, are the most commonly observed extra chromosomes in high hyperdiploidy, yet neither chromosome appears to be directly associated with improved prognosis. Conversely, trisomy for chromosome 1 occurs less frequently (B6%) but correlates strongly with favorable prognosis, as demonstrated in this study and others. 6 8 Mechanisms to explain the favorable prognosis of good trisomy patients are not known. Hyperdiploid B-precursor lymphoblasts have stringent survival requirements and a marked propensity to undergo apoptosis, 27,28 a finding that might explain the paradox of the higher percentage of proliferating cells but lower white blood cell count generally observed in ALL patients. 29 Ito et al 29 concluded that leukemic cell growth parameters strongly influence response to treatment and this suggests the hyperdiploid blast cells may have increased sensitivity to lower levels of therapeutic agents. However, Ito et al 29 specifically considered the subset of ALL cases with trisomy 4 and 1 but found no difference in cellular survival as suggested by data indicating specific trisomies predict better outcome. Despite the overwhelming number of studies substantiating increased chromosome copy number with low risk and good survival, 8,12,13,15,17,18,3 some investigators have been unable to confirm these findings. 2,31 The Dutch and Swedish Childhood Groups found the diagnostic karyotype to be only of borderline significance as a predictor of outcome. 31,32 Donadieu et al, 3 presented data from 1552 pediatric ALL patients registered in the FRALLE protocols. Using univariate and multivariate analyses, they concluded that the predictive power of chromosome analysis was only 1.6. There were no definitive explanations but they suggested contributory factors for these discrepancies included differences in patient number and characteristics, treatments, follow-up and lack of stratification among the leukemia study groups for such variables as cutoff points, coding, and missing data. This paper represents the accumulated efforts of two major groups, the CCG and POG, since 1988 and 1986 respectively, presented by the new collaborative COG. It is generally accepted that analysis of data is enhanced when subjected to larger population representation, extension of study period, and reduction in patient selection ascertainment bias. With respect to the data presented here, the two former groups independently assessed the effect of trisomies 4, 1, and 17 on outcome in each of two NCI risk groups. The patients were treated according to the different protocols of the two groups yet despite these differences, the two groups demonstrated significant association between the simultaneous occurrence of trisomies 4, 1, and 17 in leukemic cells with respect to EFS of children with Standard Risk, B-precursor ALL. The COG ALL Risk Group/Classification Subcommittee has used these findings for risk group planning to direct treatment assignments in the new COG ALL protocols. 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