Risk Of Childhood Acute Lymphoblastic Leukemia Research Articles

Etiology of common childhood acute lymphoblastic leukemia: the adrenal hypothesis

The pattern of infections in the first years of life modulates our immune system, and a low incidence of infections has been linked to an increased risk of common childhood acute lymphoblastic leukemia (ALL). We here present a new interpretation of these observations--the adrenal hypothesis--that proposes that the risk of childhood ALL is reduced when early childhood infections induce qualitative and quantitative changes in the hypothalamus-pituitary-adrenal axis that increase plasma cortisol levels. This may directly eliminate leukemic cells as well as preleukemic cells for the ALL subsets that dominate in the first 5-7 years of life and may furthermore suppress the Th1-dominated proinflammatory response to infections, and thus lower the proliferative stress on pre-existing preleukemic cells.

MDR1 C3435T Polymorphism in Mexican Children with Acute Lymphoblastic Leukemia and in Healthy Individuals

To determine the influence of the MDR1 C3435T polymorphism on the development of childhood acute lymphoblastic leukemia (ALL), we studied 107 children with ALL and 111 healthy subjects. All subjects were genotyped for the C3435T polymorphism using the polymerase chain reaction-restriction fragment length polymorphism method. The genotype frequencies in the patients were 17% homozygous CC, 61% heterozygous CT, and 22% homozygous TT; in healthy individuals the genotype frequencies were 14% CC, 53% CT, and 33% TT. In patients with ALL the allele frequencies were 0.47 for the C allele and 0.53 for the T allele; in the healthy group these allele frequencies were 0.40 and 0.60 for the C and T alleles, respectively. No significant differences in allele frequency (p > 0.176) and genotype frequency (p > 0.255) were detected between the two groups. These findings suggest that the CT or TT genotype does not increase the risk for childhood ALL in Mexican patients. On the other hand, significant differences in allele frequencies were detected in the comparison of Mexican healthy subjects with other populations. Whether these differences are fortuitous or related to diverse genetic backgrounds remains to be elucidated.

MDR1 C3435T Polymorphism in Mexican Children with Acute Lymphoblastic Leukemia and in Healthy Individuals

To determine the influence of the MDR1 C3435T polymorphism on the development of childhood acute lymphoblastic leukemia (ALL), we studied 107 children with ALL and 111 healthy subjects. All subjects were genotyped for the C3435T polymorphism using the polymerase chain reaction–restriction fragment length polymorphism method. The genotype frequencies in the patients were 17% homozygous CC, 61% heterozygous CT, and 22% homozygous TT ; in healthy individuals the genotype frequencies were 14% CC, 53% CT, and 33% TT. In patients with ALL the allele frequencies were 0.47 for the C allele and 0.53 for the T allele; in the healthy group these allele frequencies were 0.40 and 0.60 for the C and T alleles, respectively. No significant differences in allele frequency ( p > 0.176) and genotype frequency ( p > 0.255) were detected between the two groups. These findings suggest that the CT or TT genotype does not increase the risk for childhood ALL in Mexican patients. On the other hand, significant differences in allele frequencies were detected in the comparison of Mexican healthy subjects with other populations. Whether these differences are fortuitous or related to diverse genetic backgrounds remains to be elucidated.

Eligibility for allogeneic transplantation in very high risk childhood acute lymphoblastic leukemia: the impact of the waiting time

The advantage of allogeneic transplant from compatible related donors versus chemotherapy in children with very-high-risk acute lymphoblastic leukemia in first complete remission was previously demonstrated in an international prospective trial. This study quantified the impact of time elapsed in first remission in the same cohort. Of 357 pediatric patients with very-high-risk acute lymphoblastic leukemia, 259 received chemotherapy, 55 transplantation from compatible related and 43 from unrelated donors. The 5-year disease-free survival was 44.2% overall and 42.5% for chemotherapy only patients. The chemotherapy conditional 5-year disease-free survival increased to 44.4%, 47.6%, 51.7%, and 60.4% in patients who maintained their first remission for at least 3, 6, 9, and 12 months respectively. The overall outcome was superior to that obtained with chemotherapy-only at any time-point. The relative advantage of transplant from compatible related donors in very-high-risk childhood acute lymphoblastic leukemia was consistent for any time elapsed in first remission.

Significance of Genetic Polymorphisms at Multiple Loci of CYP2E1 in the Risk of Development of Childhood Acute Lymphoblastic Leukemia

Background/Aims: The molecular etiology of childhood acute lymphoblastic leukemia (ALL) is likely to involve interactions between environmental factors and genetic make up. Understanding these interactions between various predisposing genes for the risk of developing childhood leukemia is of considerable importance. CYP2E1 is a susceptible gene in this respect, especially for its capacity to bioactivate many procarcinogens including benzene and N-nitrosodimethylamine. The CYP2E1 gene possesses several polymorphisms in humans, and among them, CYP2E1*5B and *6 have been shown to be associated with increased risks of several chemical-induced diseases. There are limited and contradictory data on the association between the CYP2E1*5B variant allele and childhood ALL, and none on such associations of CYP2E1*6 and*7B variant alleles. The aim of this study was to investigate the possible association of CYP2E1*5B, *6 and *7B alleles, alone or in combination, with the risk of incidence of childhood ALL in a Turkish population. Methods: The genotypes for both polymorphisms were determined by polymerase chain reaction/restriction fragment length polymorphism techniques on 207 healthy controls and 168 patients. Results: Neither locus was associated with the occurrence of childhood ALL. On the other hand, when both CYP2E1*5B and *6 alleles were considered together, the risk of childhood ALL increased significantly (2.9-fold; OR = 2.9, 95% CI 1.0–8.5; p < 0.05). Moreover, the presence of at least 2 variant alleles of any combination increased the risk significantly 3.9 times, suggesting a combined effect (OR = 3.9, 95% CI 1.4–11.0). Conclusion: Individuals carrying combinations of CYP2E1*5B, *6 and *7B variants together are likely associated with the risk of developing childhood ALL.

Parental social contact in the work place and the risk of childhood acute lymphoblastic leukaemia

To study the possible relation between parental social contact through occupation, a marker for a child's risk of infection, and childhood acute lymphoblastic leukaemia (ALL), the parents of 294 children with ALL aged 0–14.9 years and 376 matched controls were interviewed about their jobs after their child's birth up to the age of 3 years. Job titles were assigned to a level of social contact, and an index of occupational social contact months was created using the level and the job duration. Positive interactions between this index and rural residence associated with an increased risk of childhood ALL and common ALL (c-ALL) were observed (interaction P-value=0.02 for both, using tertiles of contact months; interaction P-value=0.05 and 0.02 for ALL and c-ALL, respectively, using continuous contact months); such findings were not observed when job durations were ignored. Our data suggest that duration of parental occupation may be important when examining the association between parental social contact in the workplace and childhood leukaemia.

Genetic Polymorphisms in the Folate Pathway and Risk of Childhood Acute Lymphoblastic Leukemia (ALL): MTHFR, MTHFD1, RFC1 and TS.

Folate is critical for DNA synthesis and methylation; dysfunction in methylating enzymes may result in genomic instability and DNA damage via the nucleotide synthesis pathways. We hypothesize that perturbation in the folate metabolism pathway may alter the risk of developing childhood leukaemia. We recently reported that methylenetetrahydrofolate reductase (MTHFR 677C>T) was associated with reduced risk in childhood ALL.We aim to explore the value of a pathway approach, in this case exploring the impact of polymorphisms in multiple enzymes involved in the folate pathway, to determine its role in development of childhood ALL. As childhood ALL is highly heterogeneous and that some like TEL-AML1 and hyperdiploid subgroups have in utero origin, we postulated that the impact of folate metabolism may be greatest for in utero onset ALL. We analyzed the methylenetetrahydrofolate dehydrogenase (MTHFD1), reduced folate carrier (RFC1) and thymidylate synthase (TSER 5′-UTR 28bp repeat, TSER 3′-UTR 6bp deletion) in 360 children with ALL and 433 controls of Chinese and Malay origin (Ch=221, Mal=212). Genotyping was performed by RFLP-PCR, TEL-AML1 by RT-PCR, and hyperdiploidy either DNA index (≥1.16) or karyotyping. The latter was only available in some patients, especially in the Chinese.Using logistic regression model analysis, MTHFR 677C>T and MTHFD1 1958G>A showed significant influence on leukemia susceptibility in the Chinese (n=235, p=0.005) and Malays (n=125, p=0.032) respectively.In the Chinese cohort, MTHFR 677 CT and TT genotypes significantly decreased risk of childhood ALL as compared to CC wild type (p=0.004, OR=0.57, 95%CI=0.39–0.83), as well as in the hyperdiploidy subgroup (n=35, p=0.002, OR=0.28, 95%CI=0.12–0.65). The combined effect of RFC 80GA and AA genotypes with MTHFR 677CC wild type also decreased risk of childhood ALL in Chinese (p=0.05, OR=0.47, 95%CI=0.22–1.0). In the Malay cohort, the MTHFR 677 CT and TT genotypes played a protective role only in the TEL-AML1 subgroup (n=27) as compared to CC wild type (p=0.05, OR=0.24, 95%CI=0.06–1.0). However, interestingly MTHFD1 1958GG wild type decreased risk of childhood ALL as compared to MTHFD1 1958GA or AA genotypes (p=0.02, OR=0.54, 95%CI=1.11–3.05) when combined with MTHFR 677CC genotype. Haplotype analysis of TSER variants showed no significant effect in the 2 races.Using a candidate pathway approach, we showed that polymorphisms in the folate pathway significantly modified the risk of developing childhood ALL especially the MTHFR, MTHFD1 and RFC1. This effect may arise from different genes of the same pathway and this may be different for different races. This supports a pathway way rather than a single-gene approach towards elucidation of cancer risk in childhood ALL.

5,10-Methylenetetrahydrofolate Reductase Polymorphisms and Acute Lymphoblastic Leukemia Risk: A Meta-analysis

There is evidence supporting a role for 5-10 methylenetetrahydrofolate reductase (MTHFR) gene variants in acute lymphoblastic leukemia (ALL). To provide a more robust estimate of the effect of MTHFR polymorphisms on the risk of ALL, we did a meta-analysis to reevaluate the association between the two most commonly studied MTHFR polymorphisms (C677T and A1298C) and ALL risk. All case-control studies investigating an association between the C677T or A1298C polymorphisms and risk of ALL were included. We applied both fixed-effects and random-effects models to combine odds ratio (OR) and 95% confidence intervals (95% CI). Q-statistic was used to evaluate the homogeneity and both Egger and Begg-Mazumdar tests were used to assess publication bias. The meta-analysis of the C677T polymorphism and risk of childhood ALL included 13 studies with a total of 4,894 individuals. Under a fixed-effects model, the TT genotype failed to be associated with a statistically significant reduction of childhood ALL risk (TT versus CT + CC: OR, 0.88; 95% CI, 0.73-1.06; P = 0.18). However, individuals homozygous for the 677T allele exhibited a 2.2-fold decrease in risk of adult ALL (TT versus CT + CC: OR, 0.45; 95% CI, 0.26-0.77; P = 0.004). In both cases, no evidence of heterogeneity was observed. No association between the A1298C variant and susceptibility to both adult and childhood ALL was disclosed. Our findings support the proposal that the common genetic C677T polymorphism in the MTHFR contributes to the risk of adult ALL, but not to the childhood ALL susceptibility.

Birth characteristics and the risk of childhood leukaemias and lymphomas in New Zealand: a case-control study

BackgroundSome studies have found that lower parity and higher or lower social class (depending on the study) are associated with increased risks of childhood acute lymphoblastic leukaemia (ALL). Such findings have led to suggestions that infection could play a role in the causation of this disease. An earlier New Zealand study found a protective effect of parental marriage on the risk of childhood ALL, and studies elsewhere have reported increased risks in relation to older parental ages. This study aimed to assess whether lower parity, lower social class, unmarried status and older parental ages increase the risk of childhood ALL (primarily). These variables were also assessed in relation to the risks of childhood acute non-lymphoblastic leukaemia, non-Hodgkin's lymphomas and Hodgkin's disease.MethodsA case control study was conducted. The cases were 585 children diagnosed with leukaemias or lymphomas throughout New Zealand over a 12 year period. The 585 age and sex matched controls were selected at random from birth records. Birth records from cases (via cancer registration record linkage) and from controls provided accurate data on maternal parity, social class derived from paternal occupation, maternal marital status, ages of both parents, and urban status based on the address on the birth certificate. Analysis was by conditional logistic regression.ResultsThere were no statistically significant associations overall between childhood ALL and parity of the mother, social class, unmarried maternal status, increasing parental ages (continuous analysis), or urban status. We also found no statistically significant associations between the risks of childhood acute non-lymphoblastic leukaemia, non-Hodgkin lymphomas, or Hodgkin's disease and the variables studied.ConclusionThis study showed no positive results though of reasonable size, and its record linkage design minimised bias. Descriptive studies (eg of time trends of ALL) show that environmental factors must be important for some diagnoses. Work has been done on the risk of ALL in relation to chemicals (eg pesticides) and drugs, dietary factors (eg vitamins), electromagnetic fields and infectious hypotheses (to name some); but whether these or other unknown factors are truly important remains to be seen.

Perforin polymorphism A91V and susceptibility to B-precursor childhood acute lymphoblastic leukemia: a report from the Children's Oncology Group

Perforin plays a key role in the cytotoxicity of natural killer and cytotoxic T cells. Genetic mutations in the perforin gene (PRF1) give rise to approximately 30% cases of familial hemophagocytic lymphohistiocytosis. A frequent polymorphism, A91V (C to T transition at position 272), may impair processing of perforin protein to the active form, and has been suggested to increase susceptibility to childhood acute lymphoblastic leukemia (ALL). To investigate the role of A91V in ALL, we genotyped 2272 children with de novo ALL registered on the Pediatric Oncology Group ALL Classification study P9900 and 655 normal controls. Allele frequencies in the controls showed a very low frequency of the variant allele in blacks, 0.7% compared to 4% in white controls. In light of this, analysis was restricted to a comparison of white cases and controls only. Overall genotype frequencies were similar in white ALL cases and normal white controls (P=0.58), indicating that in contrast to the previous report, A91V polymorphism is not associated with increased risk of childhood ALL. PRF1 A91V frequency was significantly increased in children with BCR-ABL positive ALL (24 vs 8.5%; P=0.0048); however, this observation includes a relatively small number of cases and needs further exploration.

Effect of prophylactic cranial irradiation dose on CNS relapse, late cognitive decline and learning disabilities in children treated for acute lymphoblastic leukemia

9032 Background: Prophylactic cranial irradiation is still standard in treatment of high risk childhood acute lymphoblastic leukemia. In this study we assessed the effect of cranial irradiation dose of 1,800 cGy and 1200 cGy on CNS relapse as well as the late cognitive decline and learning disabilities in both groups versus a control group using neurophysiologic and psychometric studies. Methods: 42 patients treated from acute lymphoblastic leukemia and categorized to be at high risk of relapse were assessed in this study. 28 patients received prophylactic cranial irradiation at a dose of 1,800 cGy and 14 received a dose of 1,200 cGy. A control group of 42 age and sex matched normal children was also assessed. Visual and auditory P300 studies were carried out to assess high visual and auditory processing functions. Several selected subscales of Wechsler Intelligence scale for children were applied to both subgroups as well as the control group. Results: Mean age at receiving irradiation was 5.7 years. Mean testing age was 10 years. Mean follow up period was 4.6 years.There was one CNS relapse in the group who received 1,800 cGy (3.5%) and one in the group who received 1,200 cGy (7%). As compared to the control group the group of patient who received 1,800 cGy showed a high statistically significant delay in the latency and significant reduction in the amplitude of the Visual P300 (p &lt;0.001, =0.01 respectively). The Auditory P300 showed a significant delay in latency (p=0.01). In the group receiving 1,200 cGy only the latency of the visual P300 was significantly affected(p=0.01). The other parameters in the 1,200 cGy subgroup were not significantly affected. As for the psychometric studies there were significant differences in several subscales between controls and 1,800 cGy subgroup namely in similarities, total performance and picture compilation which were not found between controls and 1,200 cGy subgroup. Conclusions: These findings reflects that there is impairment in the intellectual abilities as well as visual and auditory processing functions in the subgroup receiving 1,800 cGy compared to the controls which was much less in the subgroup receiving 1,200 cGy at no significant increased protection from CNS relapse. No significant financial relationships to disclose.

Methylenetetrahydrofolate Reductase (MTHFR) C677T Polymorphism Decreases Risk of Childhood Acute Lymphoblastic Leukemia (ALL): A Study of the Chinese and Malay Population.

MTHFR plays a key role in folate metabolism by shuttling one-carbon units between nucleotide synthesis and methylation reactions. Two frequent polymorphisms in the human MTHFR gene (C677T and A1298C) confer moderate functional impairment of MTHFR activity for homozygous mutant individuals. These polymorphisms have been inconclusively shown to confer some form of protection against development of cancer. We postulate that MTHFR polymorphisms influence risk of developing childhood ALL by comparing the frequency of these polymorphisms in normal controls and children with ALL in their specific races. As the frequencies of these polymorphisms are unknown in Chinese and Malays populations, we performed a population study among Chinese and Malay populations, and children with ALL. A total of 310 childhood ALL were enrolled between 1992–2005 (NUH-ALL 92, HK-ALL 98, MASPORE-ALL 2003). The cases comprise of 202 Chinese ALL (B-lineage=180, T-lineage=15, infant=7) and 108 Malay ALL (B-lineage=98, T-lineage=3, infant=7). A total of 231 cases (Ch=144, Mal=87) were screened for TEL-AML1 and MLL rearrangements using RT-PCR. Umblical cord bloods (anonymous) were used as controls. Genotyping was carried out using PCR/RFLP. The frequencies of MTHFR polymorphisms were distinctly different among the Chinese and Malay populations. 54.2% of the Chinese population was either heterozygous (45%) or homozygous (9.2%) for MTHFR C677T while only 25.5% of the Malay population were either heterozygous (23.9%) or homozygous (1.6%). The frequency of MTHFR C677T polymorphism among the ALL patients were significantly different from the normal population (Chinese p=0.01, Malay p= 0.068). Specifically, the frequencies of heterozygous and homozygous for C677T among ALL patients were lower compared to the normal population: Chinese ALL 33.7% and 8.9%; Malays ALL 15.7% and 1%. The protection against childhood ALL seems to be conferred to reducing the risk of developing TEL-AML1 subtype (Table 2). This may explain the reason why the frequency of TEL-AML1 subtype is lower among the Chinese compared to the Malays (24/144 [16.7%] Chinese vs 22/87 [25.3%] Malays). No significant association of MTHFR A1298C with risk of childhood ALL. Our findings suggested that MTHFR C677T significantly reduces the risk of developing childhood leukaemia especially those with onset in utero.Table 1:Frequency of the MTHFR C677T genotypes in childhood ALL and controls(A) ChineseGenotypeControls (n=262)ALL (n=202)OR(95%CI)pCC119(45.4%)116(57.4%)1.0(referent)-CT or TT143(54.2%)86(42.6%)1.6(1.1–2.3)0.01(B) MalaysControls(n=251)ALL(n=108)CC187(74.5%)90(83.3%)1.0(referent)-CT or TT64(25.5%)18(16.7%)-0.068Table 2:Distribution of MTHFR C677T genotypes in the 3 subgroups.(A) ChineseControlsTEL-AML1 or MLLTEL-AML1 or MLLHyperdiploidyNon-hyperderploidyGenotype(n=262)Present(n=32; MLL=8/32)Absent(n=112)(n=22)(n=50)CC119(45.4%)19(59.3%)62(55.4%)16(72.7%)26(52%)CT or TT143(54.2%)13(40.6%) p=0.04550(44.7%) p=0.1296(27.3%) p<0.000124(48%) p=0.24(B) MalaysGenotypeControls(n=251)Present(n=26; MLL=4/26)Absent(n=61)CC187(74.5%)24(92.3%)48(78.7%)No DataNo DataCT or TT64(25.5%)2(7.7%) p=0.00113(21.3%) p=0.27

Gene Signatures Predictive of Outcome in Higher Risk Childhood Acute Lymphoblastic Leukemia (ALL).

The use of risk adapted therapy has improved outcome for children with ALL and assessment of early response (ER) has been used to identify a subset of patients who benefit from augmented treatment. In spite of these advances, the majority of treatment failures occur in a “good risk” subset indicating the critical need for better predictors of outcome. We performed oligonucleotide microarrays on 99 B-precursor patients treated on CCG 1961 for high risk ALL to identify: 1) genetic pathways that play a role in early response to therapy (42 day 7 rapid (R)ER, 40 slow (S)ER) and 2) a signature that would predict event free survival (28 pts > 4 yr CCR, 31 relapses < 3 yrs). RNA was extracted and amplified before hybridization to Affymetrix U133 Plus 2.0 microarrays representing over 47,000 transcripts. Data were normalized, filtered and then analyzed by both unsupervised and supervised methods. We identified a robust signature that predicted SER at day 7 (79% of cases in a test set) but not RER thus limiting its utility in risk stratification. Furthermore, we also identified a highly significant set of genes that correlated with SER (M2/M3) at day 14. Importantly, expression of 47 probe sets were significantly different in patients who were in CCR for more than 4 years compared to cases that experienced a relapse within the first 3 years (FDR ≤0.05%). Logistic regression indicated that each of the 47 probe sets has significant prognostic value beyond that contained in the clinical covariates (including gender, age and WBC count). A major subset of these genes were involved in signal transduction (MAP3K3, YWHAZ, PCTK2, TGFBR1, PTPRE, IFNGR2, HSPA8). In a separate validation analysis, subsets of genes were selected using logistic regression with backward, forward and stepwise variable selection and the models proved to be significantly predictive of response in the independent expression data set of 220 patients generated previously using a smaller probe set with U95Av2 microarrays (Mosquera-Caro et al, Blood 2003, 102(11)). Interestingly, the genetic models superseded clinical co-variates such as age, WBC and gender. Finally, to assess further the predictive accuracy of these gene signatures, we randomly divided the data set into a training set (2/3 cases) that was used to develop a signature predictive of relapse that was tested for accuracy in the remaining cases (1/3 cases). This was repeated three times. On average, 77% of patients in CCR and 73% of patients who relapsed were accurately classified in the test set. With further validation these signatures of outcome (not early response) will allow for more precise identification of patients who are at very high risk for relapse and may provide a mechanistic understanding of why patients fail therapy.

Simplifying Complex Microarray Data To Derive Gene Expression Profiles Which Identify Childhood Acute Lymphoblastic Leukaemia Patients at Risk of Relapse.

The optimal treatment of patients with childhood acute lymphoblastic leukaemia (ALL) depends on establishing accurate diagnosis. Our investigations seek to strategically develop the application of microarray gene expression profiling to identify ALL patients with clinically homogenous presentations but which may respond differently to established treatment regimens. We have determined the gene expression profiles of ALL bone marrow (BM) samples taken from patients at diagnosis. Data analysis has focussed on the use of a novel and innovative statistical technology, Gene-RaVE. This series of patent protected algorithms builds a multinomial regression model using Bayesian variable selection. Gene-RaVE leads to the generation of a parsimonious and simple diagnostic gene expression signature, but which provides increased predictive ability over current analysis approaches. We describe our analysis of both Affymetrix (HU133A) and cDNA (10.5K) microarray gene expression profiles generated from diagnostic BM from >100 ALL patients covering the broad ALL subtypes including T and B lineage as well as T cell lymphoma leukaemia. Comparison of gene expression data failed to identify clearly distinguishing profiles between patients identified as ‘standard risk' from ‘medium risk' according to BFM95 clinical criteria. Gene expression profiles from a cohort of ALL patients, identified as ‘standard risk' at diagnosis, were compared on the basis of their overall clinical outcome: relapse within 2 yrs vs non-relapse. Using a range of analyses including t-test, Gene-RaVE, discriminant analysis approaches and principle component analysis, we have discovered that small subsets of genes (<10), all of which included Nedd4BP3 and Ribosomal Protein L38 (RPL38), can be used to distinguish the two outcome groups. Subsequent validation using real time PCR supports the increase in Nedd4BP3 expression in standard risk patients which do not respond well to established treatment regimens. The Gene-RaVE algorithm also provides a generic framework for survival analysis. This approach indicates that the expression of these Nedd4BP3, RPL38 and inositol 1, 4, 5-triphosphate receptor, type 2 can be used to build a survival ‘index' which correlates with the time to a relapse event in standard risk childhood ALL patients. Our results are suggestive of a way forward in the development of an informative, yet efficient diagnostic tool for this childhood malignancy using microarray gene expression analysis technology.

Long-Term Results of a Randomized Trial on Extended Use of High Dose l-Asparaginase for Standard Risk Childhood Acute Lymphoblastic Leukemia

Between September 1991 and May 1997, within the International Berlin-Frankfurt-Muenster Study Group (I-BFM-SG), a randomized study was performed aimed at assessing the efficacy of prolonged use of high-dose l-asparaginase (HD-l-ASP) during continuation therapy in children with standard risk (SR) acute lymphoblastic leukemia (ALL), treated with a reduced BFM-type chemotherapy. The Italian, Dutch, and Hungarian groups participated in this study denominated IDH-ALL-91, and 494 children were enrolled. Treatment consisted of a BFM-type modified backbone with omission of the IB part in induction and elimination of two doses of anthracyclines during reinduction in both arms at the beginning of continuation therapy. Patients were randomly assigned to receive (YES-ASP) or not (NO-ASP) 20 weekly HD-l-ASP (25,000 IU/m2). The event-free-survival and overall survival probabilities at 10 years for the entire group were 82.5% (1.8) and 90.3% (1.3), respectively. Of the 490 patients eligible for random assignment, 355 (72.4%) were randomly assigned (178 YES-ASP and 177 NO-ASP). After a median follow-up of 9 years, the probability of disease-free survival at 10 years was 87.5% (SE, 2.5) for YES-ASP arm versus 78.7% (SE, 3.3) for NO-ASP arm (P = .03). In multivariate analysis, NO-ASP arm (P = .03), male sex (P = .004), and age older than 10 years (P = .0003) had a significantly adverse impact on outcome. In this subset of patients, selected with criteria not including monitoring of minimal residual disease, application of extended HD-l-ASP may improve prognosis, compensating reduced leukemia control that results from adoption of a reduced-intensity BFM-backbone for treatment of children with SR ALL.

Ethnic Difference in Daycare Attendance, Early Infections, and Risk of Childhood Acute Lymphoblastic Leukemia

A role for infectious agents has been proposed in the etiology of childhood acute lymphoblastic leukemia (ALL), particularly for common ALL (c-ALL; ALL diagnosed in children ages 2-5 years and expressing CD10 and CD19 surface antigens). We evaluated the possible etiologic role of daycare attendance (a proxy measure for exposure to infectious agents) and infections during infancy in the Northern California Childhood Leukemia Study. A total of 294 incident ALL cases (ages 1-14 years) and 376 individually matched controls were included in this analysis. In non-Hispanic White children, daycare attendance measured by child-hours was associated with a significantly reduced risk of ALL. Compared with children who did not attend any daycare, the odds ratio (OR) for those who had >5,000 child-hours during infancy was 0.42 [95% confidence interval (95% CI), 0.18-0.99] for ALL and 0.33 (95% CI, 0.11-1.01) for c-ALL. Test for trend is also significant, which supports a dose-response relationship. The magnitude of effect associated with the same number of child-hours was stronger for daycare attendance during infancy than for daycare attendance before diagnosis. In addition, self-reported ear infection during infancy was associated with a significantly reduced risk of c-ALL (OR, 0.32; 95% CI, 0.14-0.74) in non-Hispanic White children. In Hispanic children, no association was observed among daycare attendance, early infections, and risk of childhood ALL or c-ALL. These results offer indirect yet strong support for the infectious disease hypothesis in the etiology of ALL in non-Hispanic White children and highlight an important ethnic difference.

Polymorphisms of drug‐metabolizing enzymes and risk of childhood acute lymphoblastic leukemia

The involvement of phase I and II enzymes is well documented in the metabolism of a wide range of drugs and xenobiotics. Single-nucleotide polymorphisms (SNPs) of these enzymes are also known to alter their protein expression and function. Moreover, genetic susceptibility and environmental exposure have been proposed to be an etiology of cancer. We hypothesized that polymorphisms of these enzymes might affect the risk of childhood acute lymphoblastic leukemia (ALL). CYP 1A1, CYP 3A4*1B, CYP 3A5*3, CYP 3A5*6, GSTM1, and GSTT1 polymorphisms were genotyped by using PCR-RFLP in 107 children with ALL and 320 healthy controls. Allele and genotype frequencies of each of the SNPs were compared between two groups. It was found that the allele frequencies of CYP 1A1*1, *2A, *2B, and *4 were not different between cases and controls. CYP 3A4*1B allele frequency was only 0.8% and 0.9% in ALL and controls, respectively. CYP 3A5*1/*1, *1/*3, and *3/*3 genotype frequencies showed no statistically significant difference between patients and controls. CYP 3A5*6 was not detected in our population. The GSTM1 null genotype was significantly increased in children with ALL (OR 1.7; 95% CI, 1.0, 2.7). In contrast, the GSTT1 null genotype did not show this effect. Our data thus demonstrate that the GSTM1 null genotype might increase the risk of childhood ALL in a Thai population.

Single Nucleotide Polymorphisms of DNA Synthetic and Repair Enzymes and Risk of Childhood Acute Lymphoblastic Leukemia.

Although the outcome of children with acute lymphoblastic leukemia (ALL) has been improving, the origin of this disease is still unknown. It is likely that individual genetic susceptibility and environmental exposure play a role in carcinogenesis. To maintain normal hematopoiesis, DNA synthesis and repair systems need to be intact. Folate metabolism, producing purines and pyrimidines, is the source of nucleotides while base excision and nucleotide excision repair enzymes, i.e. XRCC1 and XPD, have important roles in protection of DNA damage. Single nucleotide polymorphisms (SNPs) of enzymes involving these processes alter their enzymatic structures and functions. We hypothesized that SNPs of folate metabolic enzymes including methylenetetrahydrofolate reductase (MTHFR 677 C>T; 1298 A>C), methionine synthase (MS 2756 A>G), and tandem repeats of thymidylate synthase (TS 2R or 3R) and of DNA repair enzymes (XRCC1 26304 C>T; 27466 G>A; 28152 G>A and XPD 23591 G>A; 35931 A>C) could effect the risk of ALL in children. We performed genotyping of these SNPs in 108 ALL and 317 normal controls by using PCR RFLP method. Genotype frequencies of folate metabolic enzymes SNPs were not different between cases and controls. However, TS 2R allele showed a trend to decrease risk of ALL (OR=0.66; 95% CI 0.41–1.07). We observed a 4.5 fold reduction in the risk of ALL in individuals with the XRCC1 26304 TT genotype (OR=0.22; 95% CI 0.5–0.96). XRCC1 26304 T allele showed a protective effect to this disease (OR=0.67; 95% CI 0.47–0.97). In contrast, individuals with XRCC1 28152 A allele had an increased risk of ALL (OR=1.67; 95% CI 1.2–2.33) compared to those with G allele. XRCC1 28152 GA and GA+AA genotypes were significantly higher among patients with ALL compared to controls (OR=2.17; 95% CI 1.37–3.45 and OR=2.18; 95%CI 1.38–3.42). No association between genotype or allele frequencies of both XPD SNPs and risk of ALL was shown in this study. In conclusion, our data demonstrated that SNPs of DNA repair enzymes (XRCC1 26304 C>T and 28152 G>A) but not folate-dependent DNA synthetic enzymes may influence risk of childhood ALL.

Role of MRD Monitoring in Childhood Acute Lymphoblastic Leukemia after Allogeneic Transplantation.

Relapse of acute lymphoblastic leukemia (ALL) after allogeneic transplant has very poor prognosis; whether early prediction of relapse by means of minimal residual disease (MRD) analysis could allow effective treatment is still to be assessed. Eighteen patients at high risk of relapse were prospectively monitored in a single transplant center. MRD analysis and clinical follow up were completed for the first series of 11 patients. This includes 9 males and 2 females (median age 11ys, range 2–16) who received allogeneic hematopoietic cell transplantation (HCT) from compatible (5), one locus mismatched (1) or haploidentical (1) related or unrelated (4) donor for ALL in 1st (5), 2nd (4), or 3rd (2) complete remission (CR), after conditioning regimen containing total body irradiation (TBI) and etoposide (9) or others, and GVHD prophylaxis consisting of cyclosporine, associated with ATG in transplant from other than compatible related donor. Grafts consisted of unmanipulated bone marrow (9), containing a median of 6.6x106CD34+/Kg (range 1.7–8.6) and 57.2x106CD3+/Kg (range 24.4–96.2), or peripheral (1), containing 11x106CD34+/Kg and 174x106CD3+/Kg, or positively selected peripheral (1) containing 12x106CD34+/Kg and 0.04x106CD3+/Kg. Five patients developed grade II–IV acute GVHD, requiring ATG in 4 cases. Five of 11 patients are alive in CR at a median of 15 months (range 11–21), 1 died in CR at 7 months, 5 relapsed at a median of 8 months (range 3–23), and 3 of them died. Patients were monitored by clone-specific RQ-PCR of one (4) or two (7) Ig/TcR markers, with a sensitivity of at least 10−4. At the time of transplant 7 patients were positive at the analysis of the MRD, while 4 were negative; patients were monitored at 1, 3, 6, 9 and 12 months after transplantation, or according to clinical requirements. Among the 4 MRD negative patients, 1 remained negative and is in CR at 19 months, 1 became positive 6 months after unrelated transplant and relapsed 2 months later, 1 relapsed 30 months after haploidentical transplant, a long time after MRD monitoring had stopped, while 1 died in CR. Among the 7 MRD positive patients, 2 remained always MRD positive and relapsed 3 and 7 months after transplant, and 5 experienced MRD negativity at a certain time after transplant; 1 of 5 became MRD positive at the 6th month after transient negativity and relapsed 3 months later, 3 of 5 became negative since the 1st or 3rd month, remained negative, and are alive in CR at 9, 12, and 13 months after transplant, while the remaining 1 alternated negative and positive MRD results and is in CR at 6 months. In 5 patients quantitative MRD data allowed early immunosuppression tapering or discontinuation, yielding severe GVHD in 1, and DLI treatment was planned in 2, but refused in 1; 2 of these 5 are in CR, while 3 relapsed, despite 1 experienced transient MRD 1-log reduction and 1 negativization. In conclusion, MRD monitoring after BMT might direct either early immunosuppression tapering or DLI for prevention of relapse in high risk childhood ALL transplanted patients.

Breastfeeding and the Risk of Childhood Leukemia: A Meta-Analysis

The authors used a meta-analytic technique to (1) quantify the evidence of an association between duration of breastfeeding and risk of childhood acute lymphoblastic leukemia (ALL) or acute myeloblastic leukemia (AML), (2) assess the influence of socioeconomic status (SES) on any such associations, and (3) discuss the implications of these findings for the evaluation of whether breastfeeding reduces the risk of childhood leukemia. A fixed effects model was employed to systematically combine the results of 14 case-control studies addressing the effect of short-term (< or = 6 months) and long-term (>6 months) breastfeeding on the risk of childhood ALL and/or AML. Subgroup analyses of studies that did and did not adjust for SES were also performed. A significant, negative association was observed between long-term breastfeeding and both ALL risk (odds ratio [OR]=0.76; 95% confidence interval [CI] 0.68, 0.84) and AML risk (OR=0.85; 95% CI 0.73, 0.98). Short-term breastfeeding was similarly protective for ALL and AML. Results for studies that adjusted and did not adjust for SES were not significantly different from the results for the 14 studies combined. This meta-analysis showed that both short-term and long-term breastfeeding reduced the risk of childhood ALL and AML, suggesting that the protective effect of breastfeeding might not be limited to ALL as earlier hypothesized. Potential bias introduced by different participation rates for case and control samples that differed in SES can be minimized by implementing larger case-control studies with SES-matched, population-based controls.