ALBERT

Description: Maintenance therapy is a key component of ALL treatment. Although maintenance with 6-mercaptopurine (6-MP) and methotrexate (MTX) is generally less hemato-toxic, it occasionally causes severe complications such as infections, and too long maintenance is possibly associated with lower adherence. Thus, the duration of maintenance should be as short as possible, but excess shortening of maintenance therapy leads to high relapse incidence, as shown in our previous clinical trial, the Tokyo Children's Cancer Study Group (TCCSG) L92-13 (1992 - 1995, n = 347). In this study, the shortened maintenance therapy to 6 months resulted in EFS of 59.5% at 5.5 years although OS was as good as 81.5%. Especially, higher relapse rate in standard-risk (SR) resulted in EFS of as low as 60.2% (Toyoda Y, et al. J Clin Oncol 2000). However, it should be noted that about 60% of ALL achieved continuous complete remission (CCR) with short maintenance therapy. Thus, to confirm long-term outcome of ALL with this short maintenance therapy, we conducted an extended follow up study of patients enrolled on the TCCSG L92-13. In the L92-13 trial, previously untreated children (15 years or younger) with ALL were enrolled, and were assigned to three risk groups, standard-risk (SR), high-risk (HR) and extremely high-risk (HEX), according to age at diagnosis, immunephenotype, sentinel cytogenetics and initial leukocyte count. All patients received four-drug induction, followed by consolidation therapy including re-induction. Maintenance therapy with daily 6-MP and weekly MTX was shortened to 6 months, and all treatment was discontinued at 12 months after diagnosis. The data was analyzed as of 2014 July. A median of follow up period of this extended study was 14.8 years, and the survival curve is shown in Figure 1A. Relapse was reported in 128 patients, with a median time of relapse was 1.8 years from diagnosis. EFS at 12 years for all patients was 58.7 +- 2.7% (59.2% for SR [n = 127], 57.8% for intermediate-risk [IR, n = 122], and 59.2% for high-risk [HR, n = 101]) and OS was 78.7 +- 2.2% (85.4% for SR, 80.0% for IR, and 69.0% for HR). Incidences of relapse and non-relapse mortality were 37.2 +- 2.6% and 3.2 +- 0.9%, respectively. Five patients (0 in SR group, 3 in HR group, and 2 in HEX group) developed secondary malignant neoplasms before relapse, which resulted in cumulative incidence of secondary malignancy of 0.9 +- 0.5% at 12 years. Patient gender was associated with the outcome, and female had better EFS (65.3 +- 3.7%) compared to male (52.2 +- 3.8%) (p = 0.04, Figure 1B). High-hyperdiploid (HHD) patients had relatively worse prognosis, with EFS of 50.0 +- 11.8%, although it is generally considered as good prognostic factor, and most of the relapsed HHD patients were salvaged and OS was 94.4 +- 5.4%. It is confirmed that 6 months maintenance therapy is insufficient for male, HHD, and standard risk patients. In contrast, most of patients who had been in first CR at previous analysis maintained CCR status. Our results demonstrate that short maintenance therapy can cure a substantial portion of ALL with extremely low non-relapse mortality, and that it may be possible to shorten the duration of maintenance therapy for female and non-HHD patients. This study provides precise information of leukemia biology and highlights the role of maintenance therapy. Ongoing molecular characterization of the cured patients will clarify the subset of patients who can be cured with short maintenance therapy. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

Description: Background L-asparaginase is important in successfully treating childhood acute lymphoblastic leukemia (ALL). However, some patients experience hypersensitivity, mechanisms for which have not been fully elucidated. Previous studies, predominately based on populations of European ancestry, have described L-asparaginase hypersensitivity associations with genetic variant tagging the NFATC2, GRIA1, ASNS, and HLA-DRB1genes. The aim of this study was to evaluate the association between L-asparaginase hypersensitivity and genetic variants in Japanese childhood ALL patients. Methods This study included 472 Japanese children with ALL who received E. coli derived L-asparaginase comprising 6000 U/m2 intravenously or 10000 U/m2 subcutaneously according to the Tokyo Children's Cancer Study Group (TCCSG) L84-11, L89-12, L92-13, L95-14, L99-15, L04-16, and more recent protocols. L-asparaginase hypersensitivity was defined as experience of fever, rash, and other allergic reaction after L-asparaginase infusion. Through an ongoing genome-wide association study, patient DNA from saliva were genotyped using the Illumina platform and genome-wide single nucleotide polymorphism (SNP) imputation was performed using the 1000 Genomes Project Phase I Version 3 as the reference population. Tests of association between childhood ALL and SNP genotypes across the candidate loci, NFATC2, GRIA1, and ASNS, were performed using logistic regression and assuming a log-additive model of inheritance. Results We observed 47 (10%) hypersensitivity patients, of which 32 patients could not be infused again. These L-asparaginase hypersensitivities were not associated with patients' gender and age in this population. SNPs previously reported in NFATC2 rs6021191, GRIA1 rs4958351, and ANSN rs3832526 were not significantly associated with L-asparaginase hypersensitivity (P = 0.76, 0.99, and 0.53, respectively). For confirmation, the NFATC2 rs6021191 SNP was directly genotyped in a large subset of the ALL patients, but no association was observed (P = 0.44; 377 patients). Evaluation of other variants within those genes and flanking regions showed evidence of association with rs11482430 (NFATC2, P = 0.01), rs558550699 (GRIA1, P = 0.02), and rs7803055 (ANSN, P= 0.04), although not significant after correction for multiple testing. Conclusion This lack of association with variants reported in populations of European ancestry may be influenced by ethnic specific differences in genetic structure surrounding these variants as exemplified by differences in observed minor allele frequency of the reported NFATC2 rs6021191 and GRIA1 rs4958351 SNPs in Japanese (0.11 and 0.01) and Europeans (〈 0.01 and 0.36). Moreover, the type of L-asparaginase, and/or differences in therapeutic protocol may also contribute to inconsistencies with the previous reports. There is indication of an involvement of genetic variation of NFATC2 in L-asparaginase hypersensitivity, but whether the signal is representing the same regions as the previous reports needs to be further examined. Disclosures No relevant conflicts of interest to declare.

Description: Introduction 6-mercaptopurine (6-MP) is a main component of childhood acute lymphoblastic leukemia (ALL) therapy. The sensitivity of 6-MP is associated with genetic variant of 6-MP metabolism. Recently, the NUDT15 genetic variant has been identified as a risk factor of 6-MP intolerability, and its association with 6-MP-induced toxicities and 6-MP dose in ALL patients have been reported. The frequency of NUDT15 hypomorphic variant is higher in Asian populations than in European and African populations. However, the 6-MP tolerable dose and efficacy for NUDT15-deficient patients remains clear. Our study aimed to evaluate 6-MP tolerable dose, the frequencies of 6-MP induced toxicities, and outcome in 17 ALL patients with NUDT15-deficient genotype. Methods We genotyped NUDT15 genetic variants and evaluated the patients with NUDT15 homozygous variant in Japanese childhood ALL. The NUDT15 variants V18_V19insGV, V18I, R139C, and R139H were genotyped by Sanger sequencing, and the diplotype was precisely determined. The standard initiation dose of maintenance therapy was 6-MP 40 to 50 mg/m2/day and methotrexate 25 mg/m2/week. The 6-MP-induced toxicities were graded by CTCAE version 4.0. The survival rate was estimated by the log-rank test. Results A total of 17 patients with NUDT15 diplotype of *2/*2, *2/*3, *2/*5, *3/*3, *3/*5, and *5/*5 were genotyped as NUDT15 deficient. Fifteen patients were B cell-precursor (BCP) ALL and 2 patients were T-ALL. Of the 15 BCP ALL patients, 13 were standard risk and 2 were high risk patients according to National Cancer Institute/Rome criteria. Grade 3 leukopenia and grade 4 neutropenia were observed in all 17 patients, and the median observation time were 33 (range 3-95) days and 35 (20-137) days after initiating maintenance therapy, respectively. Grade 3 ALT elevation was observed in 6 patients (35%), and median observation time was 47 (range 19-427) days after initiating maintenance therapy. Moreover, during the early consolidation phase with 6-MP, severe myelosuppression was observed in 11 of these patients. The average 6-MP dose during maintenance therapy was 7.0 (range 2.7-18.3) mg/m2/day. Moreover, 16 of these 17 patients (94%) with NUDT15 deficiency required median 66 (range 5-376) days of therapy interruption. Notably, the average 6-MP dose was 18.3 mg/m2/day, and no therapy interruption occurred during maintenance therapy in patients with NUDT15 *5/*5 diplotype. Therefore, the degree of NUDT15 deficiency influenced 6-MP tolerable dose. The effect of NUDT15 deficiency on treatment outcome was evaluated in 14 patients, who completed treatment. Three patients relapsed at 124-388 days, and two of these three patients died at 877 and 959 days after the end of maintenance therapy, respectively. The overall and event-free survival rate at 4 years were 0.75 and 0.63, respectively. Neither the average 6-MP dose nor the interruption duration was associated with these events. Conclusions NUDT15-deficient genotypes strongly influence intolerability. Patients with NUDT15 deficiency did not tolerate standard 6-MP dose, and physicians should consider reducing 6-MP dose to 7 mg/m2 to avoid therapy interruption. Conversely, NUDT15 *5/*5 genotype displayed only mild NUDT15 deficiency, and the patients with this genotype tolerated 40% of the standard 6-MP dose. Further large-scale studies should be conducted to assess the NUDT15 variant's effect on survival. Figure. Figure. Disclosures No relevant conflicts of interest to declare.

Description: Scrutiny of the human genome through evaluation of common genetic variants has revealed hundreds of disease susceptibility loci. In childhood acute lymphoblastic leukemia (ALL), six regions that have replicated in several populations are now considered known susceptibility loci (ARID5B, IKZF1, CEBPE, CDKN2A, PIP4K2A, and GATA3), but their effects have yet to be fully confirmed in populations of non-European ancestry. Targeted validation attempts based on the same SNPs originally identified in European ancestral populations have been performed in East Asians, but findings have been inconsistent. This may be due to differences in linkage disequilibrium patterns, allele frequency, and/or magnitude of effect between Europeans and East Asians; thus a comprehensive characterization of genetic variation across the targeted genetic loci is required for an appropriate validation attempt in different populations. Using a large network of hospitals within the Tokyo Children's Cancer Study Group, saliva samples from previously diagnosed childhood ALL patients (aged 0-19 years) were collected between December 2012 and May 2015. Genome-wide single nucleotide polymorphism (SNP) genotyping was performed and resulted in the inclusion of a total of 570 ALL patients, with genetic data available for up to about 500,000 SNPs after quality control exclusions. Control genome-wide data were available for 2,712 previously genotyped samples from the Nagahama Study Group and Aichi Cancer Center Study, Japan. SNP imputation was performed on the combined case-control dataset using ShapeIT and Minimac3, and the 1000 Genomes Project Phase I Version 3 as the reference population. Tests of association between childhood ALL and all available SNP genotypes across the six genes (mentioned above) implicated in previous genome-wide association studies was performed using logistic regression and assuming a log-additive model of inheritance. Of the six genomic regions examined, SNPs within the IKZF1, ARID5B, and PIP4K2A genes showed a statistically significant association with childhood ALL risk after Bonferroni correction. SNPs with the strongest evidence of association for these three genes included rs7090445 (ARID5B, OR=1.75, P =3.7x10-17), rs12533431 (IKZF1, OR=1.43, P =4.3x10-5), and rs11013045 (PIP4K2A, OR=0.76, P =9.5x10-5). Further examination of these regions indicated a second independently associated locus within ARID5B. Furthermore, we observed that the same previously reported primary ALL susceptibility SNPs for IKZF1 (e.g. rs4132601, rs11978267) and PIP4K2A (e.g. rs10828317, rs7088318) were not associated in Japanese. This highlights the importance of considering regional genetic variation comprehensively when testing the role of previously implicated candidate regions in a different racial/ethnic population. Characterization of the role of CEBPE, CDKN2A, and GATA3 genetic variation in Japanese may benefit from greater statistical power and potentially additional coverage of SNPs within these regions. Disclosures No relevant conflicts of interest to declare.