Effects of methylenetetrahydrofolate reductase and reduced folate carrier 1 polymorphisms on high-dose methotrexate-induced toxicities in children with acute lymphoblastic leukemia or lymphoma

The effects of genetic polymorphism on toxicity and pharmacokinetics of methotrexate in Egyptian adult patients with leukaemia or lymphoma

Polymorphisms in genes coding folate-metabolising enzymes might alter the pharmacokinetics and sensitivity for methotrexate "MTX".The aim of the study aimed to investigate the influence of MTHFR C677T, DHFR19 Ins/del, GGH -401 C > T, and MTR A2756G polymorphisms on MTX toxicity and pharmacokinetics in Egyptian patients with Acute lymphoblastic leukaemia (ALL) or Non-Hodgkin lymphoma (NHL).Fifty adult Egyptian patients with ALL and NHL, treated with high dose MTX, were prospectively enrolled in the study. Clinical and biochemical data was collected objectively from medical records after each cycle of MTX. Plasma concentrations of MTX were measured after 72 h of initiation of infusion. Genotyping was done with a PCR-ARMS and PCR-RFLP assays.The MTHFR C677T T variants significantly increased the risk of leukopoenia, whereas the genotype MTHFR 677 C > T TT significantly associated with lymphocytopenia, thrombocytopenia, and anaemia. The genotype GGH-401 TT was significantly correlated with anaemia. Plasma MTX level was significantly higher in patients with MTR A2756G G variants.MTHFR polymorphism played the main role in MTX toxicities. The pharmacokinetics of MTX was affected by MTR polymorphism. GGH mutation was mainly concerned with anaemia. Pharmacogenetic testing are recommended to optimise MTX therapy.

Ethnic-specific predictors of neurotoxicity among patients with pediatric acute lymphoblastic leukemia after high-dose methotrexate

BACKGROUND

High-dose methotrexate (HD-MTX; 5000 mg/m2 ) is an important component of curative therapy in many treatment regimens for high-risk pediatric acute lymphoblastic leukemia (ALL). However, methotrexate therapy can result in dose-limiting neurotoxicity, which may disproportionately affect Latino children. This study evaluated risk factors for neurotoxicity after HD-MTX in an ethnically diverse population of patients with ALL.

METHODS

The authors retrospectively reviewed the medical records of patients who were diagnosed with ALL and treated with HD-MTX at Texas Children's Cancer Center (2010-2017). Methotrexate neurotoxicity was defined as a neurologic episode (e.g., seizures or stroke-like symptoms) occurring within 21 days of HD-MTX that resulted in methotrexate treatment modifications. Mixed effects multivariable logistic regression was used to estimate the odds ratio (OR) and corresponding 95% confidence interval (CI) for the association between clinical factors and neurotoxicity.

RESULTS

Overall, 351 patients (58.1% Latino) who received 1183 HD-MTX infusions were evaluated. Thirty-five patients (10%) experienced neurotoxicity, 71% of whom were Latino. After adjusting for clinical risk factors, the authors observed that serum creatinine elevations ≥50% of baseline were associated with a three-fold increased odds (OR, 3.32; 95% CI, 0.98-11.21; p = .05) for neurotoxicity compared with creatinine elevation <25%. Notably, predictors of neurotoxicity differed by ethnicity. Specifically, Latino children experienced a nearly six-fold increase in neurotoxicity odds (OR, 5.80; 95% CI, 1.39-24.17; p = .02) with serum creatinine elevation ≥50% compared with creatinine elevation <25%.

CONCLUSIONS

The current findings indicate that serum creatinine elevations ≥50% may be associated with an increased risk for neurotoxicity among Latino children with ALL and may identify potential candidates for therapeutic or supportive care interventions.

Evaluation of cytogenetic and molecular markers with MTX-mediated toxicity in pediatric acute lymphoblastic leukemia patients

PURPOSE

Pediatric acute lymphoblastic leukemia (pALL) patients have better overall survival and methotrexate (MTX) is an effective drug used in their treatment. However, the treatment-related adverse effects (TRAEs) have a bigger impact on the therapy. In this study, we have evaluated the association of polymorphisms in genes encoding proteins engaged in MTX metabolism, and the cytogenetic aberrations with TRAEs.

METHODS

A total of 115 patients between the age of 1 and 18 years (average: 6.6) under maintenance therapy were selected for the study. SLC19A1 (c.80G > A), MTHFR (c.677C > T; c.1298A > C), and TYMS (c.*450_*455del) genotypes were determined using PCR techniques and Sanger sequencing. Cytogenetic and SNP findings were analyzed for any association with the reported toxicities using odds ratio, chi-square test, multifactor dimensionality reduction (MDR) analysis for synergistic effect and, multinomial logistic regression analysis for the likelihood of adverse events.

RESULTS

Among the evaluated genetic variations, SLC19A1 (c.80G > A) was significantly associated with TRAEs (OR = 5.71, p = 0.002). Multinomial logistic regression analysis (chi-sq = 16.64, p < 0.001) and MDR analysis (chi-sq = 10.51 p < 0.001) confirmed the finding. On the other hand, no significant association was observed between adverse events and any specific cytogenetic aberration.

CONCLUSION

SLC19A1 facilitates the import of cyclic dinucleotides and reduced folates, evaluating genotypes in this gene can help in better management of patients on methotrexate treatment. Assessing a broader gene panel can help in finding more associated markers and delivering personalized medicine to the patients.

High dose methotrexate in adult Egyptian patients with hematological malignancies: impact of ABCB1 3435C > T rs1045642 and MTHFR 677C > T rs1801133 polymorphisms on toxicities and delayed elimination

High dose methotrexate (HDMTX) is an essential agent in chemotherapeutic regimens used in various hematological malignancies in Egyptian adults. The research for the impact of gene polymorphism on HDMTX induced toxicities and delayed elimination is an important ongoing objective in many studies, variable and conflicting results produced in the past years to clarify that impact. This study aimed to investigate the role of ABCB1 3435 C > T rs1045642 and MTHFR 677 C > T rs1801133 polymorphisms on HDMTX induced toxicity outcomes and delayed elimination in Egyptian adult patients with hematological malignancies. A prospective, observational cohort study was conducted on a total of 62 Egyptian adult patients with hematological malignancies age ≥ 18-years-old. All demographic, medical, and laboratory data were continuously collected from the patients' medical files in an up-to-date follow-up in selected clinics during the period from April 2018 to March 2020. Venous blood samples were collected for the purpose of genotyping, DNA extraction, and measurement of MTX levels. All the relevant data were statistically analyzed. The studied patients' median age was 25 years old with a range of (18-62) years. Forty-six patients were males with about 74%, and 16 were females with about 26%. Eighty-nine percent of the patients diagnosed with acute lymphoblastic leukemia 'ALL', 5% of the patients had B cell non-hodgkin lymphoma 'B-NHL' and 3% diagnosed with primary central nervous system lymphoma 'PCNSL' and Burkitt's lymphoma 'BL' Hematological, hepatic, renal and gastrointestinal toxicities observed post-HDMTX were recorded with the hematological toxicities toping on all the others, also patients with delayed elimination at 72 hours post the HDMTX dose were determined. Statistical analysis revealed a significant association between ABCB1 3435 C > T rs1045642 and HDMTX delayed elimination with about 10 times higher risk among the minor allele 'T' carriers (p-value = 0.006) (odds ratio [OR]: 10.470; 95% CI: 1.961-55.904). No significant association observed between the studied gene polymorphisms: MTHFR 677 C > T rs1801133, ABCB1 3435 C > T rs1045642, and different toxicity outcomes. According to our best knowledge, this study is the first to conclude a significant association between ABCB1 3435 C > T rs1045642 gene polymorphism and HDMTX delayed elimination at 72 hours post HDMTX infusion; also, it is the first study to analyze the association between ABCB1 3435 C > T rs1045642 polymorphism with HDMTX toxicity and delayed elimination in adult Egyptian patients with hematological malignancies.

The influence of MTHFR genetic polymorphisms on methotrexate therapy in pediatric acute lymphoblastic leukemia

MTHFR is a crucial enzyme in folate metabolism. This study aimed to determine the relationship between MTHFR genetic polymorphism and elimination and toxicities of methotrexate (MTX). To do that, the study enrolled 145 patients diagnosed with acute lymphoblastic leukemia, who received chemotherapy following the Chinese Children’s Cancer Group Acute Lymphoblastic Leukemia (CCCG-ALL)-2015 protocol (clinical trial number: ChiCTR-IPR-14005706). We analyzed the effects of MTHFR C677T and A1298C polymorphisms on MTX elimination and toxicities. Patients with the MTHFR C677T TT genotype could tolerate a significantly higher MTX dose than those with the CC/CT genotype. However, patients with C677T TT genotypes had an increased risk of hypokalemia (1.369 to CC and 1.409 to CT types). The MTX infusion rate in patients with the MTHFR A1298C AC genotype was slightly lower than that in those with CC or AA genotypes. Patients with the A1298C AA genotype had a 1.405-fold higher risk of hepatotoxicity than those with the AC genotype (P > 0.05). There was no significant difference between the prevalence of other toxicities among MTHFR C677T or A1298C genotypes (P > 0.05). Neither MTHFR C677T nor A1298C polymorphisms were significantly associated with delayed MTX clearance. To conclude, MTHFR polymorphisms were not good predictors of MTX-related toxicities.

The Role of Genetic Polymorphisms in High-Dose Methotrexate Toxicity and Response in Hematological Malignancies: A Systematic Review and Meta-Analysis

Objective: High-dose methotrexate (HDMTX) is a mainstay therapeutic agent for the treatment of diverse hematological malignancies, and it plays a significant role in interindividual variability regarding the pharmacokinetics and toxicity. The genetic association of HDMTX has been widely investigated, but the conflicting results have complicated the clinical utility. Therefore, this systematic review aims to determine the role of gene variants within the HDMTX pathway and to fill the gap between knowledge and clinical practice. Methods: Databases including EMBASE, PubMed, Cochrane Central Register of Controlled Trials (CENTRAL), and the Clinical Trials.gov were searched from inception to November 2020. We included twelve single-nucleotide polymorphisms (SNPs) within the HDMTX pathway, involving RFC1, SLCO1B1, ABCB1, FPGS, GGH, MTHFR, DHFR, TYMS, and ATIC. Meta-analysis was conducted by using Cochrane Collaboration Review Manager software 5.3. The odds ratios (ORs) or hazard ratios (HRs) with 95% confidence interval (95% CI) were analyzed to evaluate the associations between SNPs and clinical outcomes. This study was performed according to the PRISMA guideline. Results: In total, 34 studies with 4102 subjects were identified for the association analysis. Nine SNPs involving MTHFR, RFC1, ABCB1, SLCO1B1, TYMS, FPGS, and ATIC genes were investigated, while none of studies reported the polymorphisms of GGH and DHFR yet. Two SNPs were statistically associated with the increased risk of HDMTX toxicity: MTHFR 677C>T and hepatotoxicity (dominant, OR=1.52, 95% CI=1.03-2.23; recessive, OR=1.68, 95% CI=1.10-2.55; allelic, OR=1.41, 95% CI=1.01-1.97), mucositis (dominant, OR=2.11, 95% CI=1.31-3.41; allelic, OR=1.91, 95% CI=1.28-2.85), and renal toxicity (recessive, OR=3.54, 95% CI=1.81-6.90; allelic, OR=1.89, 95% CI=1.18-3.02); ABCB1 3435C>T and hepatotoxicity (dominant, OR=3.80, 95% CI=1.68-8.61), whereas a tendency toward the decreased risk of HDMTX toxicity was present in three SNPs: TYMS 2R>3R and mucositis (dominant, OR=0.66, 95% CI=0.47-0.94); RFC1 80A>G and hepatotoxicity (recessive, OR=0.35, 95% CI=0.16-0.76); and MTHFR 1298A>C and renal toxicity (allelic, OR=0.41, 95% CI=0.18-0.97). Since the data of prognosis outcomes was substantially lacking, current studies were underpowered to investigate the genetic association. Conclusions: We conclude that genotyping of MTHFR and/or ABCB1 polymorphisms prior to treatment, MTHFR 677C>T particularly, is likely to be potentially useful with the aim of tailoring HDMTX therapy and thus reducing toxicity in patients with hematological malignancies.

Systematic Review of Pharmacogenetic Factors That Influence High-Dose Methotrexate Pharmacokinetics in Pediatric Malignancies

Methotrexate (MTX) is a mainstay therapeutic agent administered at high doses for the treatment of pediatric and adult malignancies, such as acute lymphoblastic leukemia, osteosarcoma, and lymphoma. Despite the vast evidence for clinical efficacy, high-dose MTX displays significant inter-individual pharmacokinetic variability. Delayed MTX clearance can lead to prolonged, elevated exposure, causing increased risks for nephrotoxicity, mucositis, seizures, and neutropenia. Numerous pharmacogenetic studies have investigated the effects of several genes and polymorphisms on MTX clearance in an attempt to better understand the pharmacokinetic variability and improve patient outcomes. To date, several genes and polymorphisms that affect MTX clearance have been identified. However, evidence for select genes have conflicting results or lack the necessary replication and validation needed to confirm their effects on MTX clearance. Therefore, we performed a systematic review to identify and then summarize the pharmacogenetic factors that influence high-dose MTX pharmacokinetics in pediatric malignancies. Using the PRISMA guidelines, we analyzed 58 articles and 24 different genes that were associated with transporter pharmacology or the folate transport pathway. We conclude that there is only one gene that reliably demonstrates an effect on MTX pharmacokinetics: SLCO1B1.

Influence of MTHFR C677T and A1298C polymorphisms on the survival of pediatric patients with non-Hodgkin lymphoma

This study evaluated the influence of MTHFR C677T/A1298C polymorphisms on the survival of pediatric NHL. We enrolled 374 patients including 283 males and 91 females between 2014 and 2020. The median age was 9 years. The tumor types included Burkitt lymphoma (n = 180), lymphoblastic lymphoma (n = 95), anaplastic large cell lymphoma (n = 64), and diffuse large B cell lymphoma (n = 35). A subgroup of 158 patients were genotyped concerning C677T/A1298C polymorphisms. Neither C677T nor A1298C polymorphism was a significant factor in multivariate analysis. However, Kaplan-Meier analysis revealed that patients carrying 677 T allele had a significantly higher 5-year EFS rate in the whole group (n = 158), and higher 5-year EFS/OS rates in the subgroup of BL/DLBCL than those with wild type. In conclusion, the C677T polymorphism could be used for survival prediction and potential risk stratification for further treatment protocols for Chinese pediatric NHL, especially for BL/DLBCL.

Genetic variants associated with methotrexate-induced mucositis in cancer treatment: A systematic review and meta-analysis

Methotrexate (MTX), an important chemotherapeutic agent, is often accompanied with mucositis. The occurrence and severity are unpredictable and show large interindividual variability. In this study, we review and meta-analyze previously studied genetic variants in relation to MTX-induced mucositis. We conducted a systematic search in Medline and Embase. We included genetic association studies of MTX-induced mucositis in cancer patients. A meta-analysis was conducted for single nucleotide polymorphisms (SNPs) for which at least two studies found a statistically significant association. A total of 34 SNPs were associated with mucositis in at least one study of the 57 included studies. Two of the seven SNPs included in our meta-analysis were statistically significantly associated with mucositis: MTHFR c.677C > T (recessive, grade ≥3 vs grade 0-2, OR 2.53, 95 %CI [1.48-4.32], False Discovery Rate[FDR]-corrected p-value 0.011) and MTRR c.66A > G (overdominant, grade ≥1 vs grade 0, OR 2.08, 95 %CI [1.16-3.73], FDR-corrected p-value 0.042).

Influence of Methylenetetrahydrofolate Reductase C677T and A1298C Polymorphism on High-Dose Methotrexate-Related Toxicities in Pediatric Non-Hodgkin Lymphoma Patients

Purpose

This retrospective study aimed to investigate the relationships between the methylenetetrahydrofolate reductase (MTHFR) C677T/A1298C and high-dose methotrexate (HD-MTX)-related toxicities in pediatric non-Hodgkin lymphoma (NHL) patients.

Patients and Methods

We reviewed the medical records of 93 NHL patients aged under 18 years who received HD-MTX therapy at the dose of 5 g/m² with 24-h infusion at Sun Yat-sen University Cancer Center between 2014 and 2019.

Results

There were 61 males and 32 females, with a median age of 8.8 years (0.9–15.8 years). The tumor types included lymphoblastic lymphoma (n = 38), Burkitt’s lymphoma (n = 31), anaplastic large cell lymphoma (n = 18), diffuse large B-cell lymphoma (n = 6). Overall, 355 courses of HD-MTX therapy were prescribed. All patients were rescued with calcium folinate 12 h after the end of MTX infusion. We found that plasma MTX levels > 0.2 μmol/L at 48 h post-infusion increased the risk of developing oral mucositis (2.4% VS. 9.5%, P = 0.018). Also, patients carrying the C677T and T677T genotypes had tendencies to be more susceptible to oral mucositis (P = 0.034). Patients harboring mutant 677T allele were more likely to develop leucopenia (38.5 vs. 50.3%, P = 0.025) and thrombocytopenia (22.0 vs. 32.4%, P = 0.028). For polymorphism A1298C, the mutant genotype played a protective role in vomiting (11.1 vs. 4.3%, P = 0.018) but increased the risk of anemia (23.8 vs. 41.7%, P < 0.001) and leucopenia (38.1 vs. 50.3%, P = 0.021).

Conclusion

Childhood NHL patients harboring C677T genotype were more vulnerable to oral mucositis, leucopenia, and thrombocytopenia, while those with A1298C genotype were at a decreased risk of vomiting and more likely to develop anemia and leucopenia.

Factors Predicting Severe Myelosuppression and Its Influence on Fertility in Patients with Low-Risk Gestational Trophoblastic Neoplasia Receiving Single-Agent Methotrexate Chemotherapy

Purpose

To investigate the potential factors to predict severe myelosuppression among low-risk gestational trophoblastic neoplasia (GTN) patients with single-agent methotrexate (MTX) chemotherapy. To analyze reproductive outcomes of patients with or without severe myelosuppression after achieving complete remission (CR).

Patients and Methods

The retrospective study included 319 low-risk GTN patients registered from January 2008 to December 2018 in our hospital. Patients were divided into two groups according to myelosuppression grading. Their clinical data and reproductive outcomes were compared and analyzed.

Results

A higher proportion of patients in group A received second-line chemotherapy than group B (P<0.001). The number of total chemotherapy courses was more in group A than group B (P=0.001), while the number of MTX chemotherapy courses was more in group B than group A (P=0.001). When the joint predictor of pretreatment albumin (ALB) was not more than 44.5 g/L, pretreatment serum creatinine (Scr) was not less than 75.6 μmol/L, and the number of MTX chemotherapy courses was not less than four, there was a moderate predictive value. There was no significant difference of reproductive outcomes between the two groups after achieving CR.

Conclusion

Although some patients developed severe myelosuppression, MTX was still the effective first-line treatment for low-risk GTN patients. Patient’s pretreatment ALB was not more than 44.5 g/L, pretreatment Scr was not less than 75.6 μmol/L, and the number of MTX chemotherapy courses not less than four could be used as combined predictors to recognize the risk of severe myelosuppression. Severe myelosuppression had no significant adverse influence on fertility after achieving CR.

Adverse effects with intravenous methotrexate in children with acute lymphoblastic leukemia/lymphoma: a retrospective study

Methotrexate (MTX) forms the backbone of maintenance cycles in childhood acute lymphoblastic leukemia (ALL) chemotherapy, including interim maintenance. There is sufficient published data describing toxicities of high dose MTX (HD-MTX), but toxicities with escalating doses of MTX (Capizzi regimen) is not well documented. Capizzi regimen is thought to be relatively safe; we contend that even low escalating doses of MTX have significant toxicities. Our study intends to characterise such events with Capizzi MTX in comparison to that seen with HD-MTX. The retrospective study was conducted at a tertiary care centre of North India. We looked for the presence of six main toxicities: febrile neutropenia, thrombocytopenia, mucositis, hepatic toxicity, renal toxicity and skin toxicity from the clinical records of children with newly diagnosed acute lymphoblastic leukemia and lymphoma (intermediate and high risk disease), treated at our centre from November 2013 to July 2018. Intermediate risk ALL (IR-ALL) received Capizzi MTX, whereas high risk ALL (HR-ALL/T-NHL), received HD-MTX. Both these regimens do not use L-asparaginase. A total of 237 cycles of Capizzi escalating MTX and 151 cycles of HD-MTX (B cell: 3 gm/m² and T cell ALL/T-NHL: 5 gm/m²) during interim maintenance were studied in 93 children. Fifty-four (54) children were of IR (all B cell ALL) and 39 of HR-ALL (21 B-ALL, 18 T-ALL/T-NHL). The combined incidence of toxicities, were similar between the two groups: 68/237 cycles (28.7%) of Capizzi MTX and 45/151 cycles (29.8%) of HD-MTX (P = 0.815). However, mucositis was more commonly witnessed in the later group at 22/151 cycle (14.6%) versus 13/237 cycles (5.5%) in Capizzi MTX (P = 0.002). Nephrotoxicity and skin toxicity was seen only in the HD-MTX group. There was no difference in the severity of toxicity, graded using NCI CTCAE v 5.0, between the two groups. There was no mortality directly attributable to methotrexate toxicity (Grade V toxicity). Serum MTX levels were available in 69/151 (45.7%) cycles of HD-MTX and showed no association with toxicity in this group. Also, there was no difference in the incidence of combined toxicities between groups with (19/69 cycles) or without (26/82 cycles) available serum MTX levels in the HR group (P = 0.577). Male gender, lower baseline ANC and lower BMI had significant association with toxicity. Methotrexate related toxicity is common with both Capizzi and HD-MTX schedule in childhood ALL with a correlation of lower BMI, baseline ANC and male gender. However, it is possible to administer Capizzi as well as HD-MTX in lower middle income countries, with manageable toxicity. Further studies will be required to substantiate our findings and determine the predictors of such events.

Polymorphisms of SLC19A1 80 G>A, MTHFR 677 C>T, and Tandem TS Repeats Influence Pharmacokinetics, Acute Liver Toxicity, and Vomiting in Children With Acute Lymphoblastic Leukemia Treated With High Doses of Methotrexate

Introduction: High dose methotrexate (HD-Mtx) is highly effective and significantly improves overall acute lymphoblastic leukemia (ALL) patients survival. The pharmacodynamics of Mtx depends on the polymorphism of genes encoding proteins engaged in the folate metabolism pathway. The aim of the current study is to determine the relationship between variants of folate metabolism-related genes and the frequency of acute toxicities of HD-Mtx. Material and Methods: A group of 133 patients aged 1.5-18.1 years (median: 6.3) was treated in accordance with the ALL-IC-2002 and ALL-IC-2009 protocols. The following polymorphisms were determined: 80 G>A SLC19A1 (solute carrier family 19 member 1; rs1051266) with direct DNA sequencing, as well as 677 C>T MTHFR (methylenetetrahydrofolate reductase; rs1801133) and the tandem repeats of the TS (thymidylate synthase) with PCR technique. HD-Mtx organ toxicities were evaluated based on the laboratory tests results and the National Cancer Institute criteria. Results: In patients with genotypes AA for SLC19A1 and CC or CT for MTHFR Mtx steady state concentrations (C_ss) and AUC_inf were distinctly higher. In patients with genotype 3R/3R for TS initial elimination rate constant was significantly higher (P = 0.003). Patients receiving Mtx at the dose of 5 g/m² had lower clearance (4.35 vs. 8.92 L/h/m²) as compared to the ones receiving 2 g/m² that indicates non-linear Mtx elimination at the higher dose. Liver impairment was the most frequently observed toxicity. The homozygous genotype was associated with a significantly higher incidence of hepatic toxicity for both the SLC19A1 (P = 0.037) and TS (P = 0.002). Logistic regression analysis indicated an increased risk of vomiting for the 2R/3R genotype of the TS gene (OR 3.20, 95% CI 1.33-7.68, P = 0.009) and for vomiting and hepatic toxicity for the 3R/3R genotype (vomiting: OR 3.39, 95% CI 1.12-10.23, P = 0.031; liver toxicity: OR 2.28, 95% CI 1.05-4.95, P = 0.038). None of the acute toxicities differed between the analyzed dosing groups. Conclusions: Determination of polymorphisms of SLC19A1, MTHFR, and TS genes might allow for a better prior selection of patients with higher risk of elevated Mtx levels. Our study is the first one to report the increased risk of hepatotoxicity and vomiting in patients with TS polymorphisms.

The effect of leucovorin rescue therapy on methotrexate-induced oral mucositis in the treatment of paediatric ALL: A systematic review

INTRODUCTION

This study aimed to determine the efficacy of different Leucovorin regimens to reduce oral mucositis in children with acute lymphoblastic leukemia after high-dose Methotrexate (HD-MTX).

METHODS

Twelve articles were included in a systematic literature review. Articles were categorized into low/medium/high risk of bias.

RESULTS

As no randomized controlled trial assessing the effect of Leucovorin has been performed, the efficacy of Leucovorin to reduce oral mucositis remains unknown. Leucovorin was initiated at 24, 36 or 42 h after HD-MTX at a dose of 15 or 30 mg/m². No meta-analysis could be performed as treatment regimens differed. When comparing studies with similar HD-MTX doses, we observed lower oral mucositis rates in regimens with higher cumulative doses of Leucovorin and early initiation of Leucovorin after MTX.

CONCLUSION

Even though future studies are necessary, higher cumulative Leucovorin doses and early initiation of Leucovorin after start of MTX seem to reduce oral mucositis.

Clinical Implications of Methotrexate Pharmacogenetics in Childhood Acute Lymphoblastic Leukaemia

Background:

In the past two decades, a great body of research has been published regarding the effects of genetic polymorphisms on methotrexate (MTX)-induced toxicity and efficacy. Of particular interest is the role of this compound in childhood acute lymphoblastic leukaemia (ALL), where it is a pivotal drug in the different treatment protocols, both at low and high doses. MTX acts on a variety of target enzymes in the folates cycle, as well as being transported out and into of the cell by several transmembrane proteins.

Methods:

We undertook a structured search of bibliographic databases for peer-reviewed research literature using a focused review question.

Results:

This review has intended to summarize the current knowledge concerning the clinical impact of polymorphisms in enzymes and transporters involved in MTX disposition and mechanism of action on paediatric patients with ALL.

Conclusion:

In this work, we describe why, in spite of the significant research efforts, pharmacogenetics findings in this setting have not yet found their way into routine clinical practice.

Predicting mucositis risk associated with cytotoxic cancer treatment regimens: rationale, complexity, and challenges

PURPOSE OF REVIEW

The goals of this review are to describe the complexity of factors influencing the risk of cancer regimen-related mucosal injury (CRRMI), to evaluate the contribution of the innate immune response to CRRMI risk, to compare the concordance of genome analytics in describing mechanism and risk, and to determine if common biological pathways are noted when CRRMI is compared to a disease with a similar phenotype.

RECENT FINDINGS

The pathogenesis of and risk for CRRMI are complex and influenced by multiple intrinsic and extrinsic factors. It is incumbent on analyses to recognize the likelihood that the interplay and cross-talk of synergistically expressed factors is critical and that the contributing weights of these factors is not uniform from patient to patient. Genomically derived analyses imply final common pathways are implicit in phenotype expression.

SUMMARY

The identification of specific factors (both genomic and otherwise) which contribute to CRRMI risk represents an important opportunity to apply principles of precision medicine to the management of regimen-related toxicities.

Systematic review of pharmacogenomics and adverse drug reactions in paediatric oncology patients

Many paediatric patients with cancer experience significant chemotherapy side effects. Predisposition to drug reactions is governed by single nucleotide polymorphisms (SNPs). We performed a systematic review of the literature from 2006 through 2016. Outcomes of interest included patient characteristics, cancer type drug of interest, genes investigated, toxicity identified and genetic polymorphisms implicated. The primary toxicities studied were neurotoxicity cardiotoxicity, osteonecrosis, and thromboembolism and hypersensitivity reactions. The retrieved studies were grouped according to toxicity reported and SNP associations. This review highlights the discoveries to date in pharmacogenomics and paediatric oncology along with highlighting some of the important limitations in the area.

Association between MTHFR microRNA binding site polymorphisms and methotrexate concentrations in Chinese pediatric patients with acute lymphoblastic leukemia

BACKGROUND

The pharmacokinetics and therapeutic response to methotrexate (MTX) display large variability in the treatment of acute lymphoblastic leukemia (ALL). The aim of the present study was to investigate the association of two microRNA (miRNA) binding site polymorphisms (rs3737966 G > A and rs35134728 DEL/TTC) in the 3'-untranslated region of MTHFR with serum MTX concentrations, in a Chinese pediatric population with ALL.

METHODS

Genotyping for MTHFR rs3737966 and rs35134728 in 144 children with ALL was performed using the Sequenom MassArray system (Sequenom, San Diego, CA, USA). Serum MTX concentrations were measured by a fluorescence polarization immunoassay 24 h (C_24h ) and 42 h (C_42h ) after administration. The effects of the polymorphisms on concentration-to-dose (C/D) ratios of MTX were assessed.

RESULTS

Complete linkage disequilibrium between rs3737966 and rs35134728 polymorphisms (r²  = 1) was found in the study population. The minor allele frequency observed in the present study (17.4%) was significantly lower than those in European and African samples reported in the 1000 Genomes Project (42.9% and 63.9%, respectively; p < 0.01). The C/D ratios of MTX at 24 and 42 h for the TTC/TTC-A/A haplotype carriers (11.74 and 0.07 μmol/l per g/m² , respectively) were significantly lower than those in DEL/DEL-G/G or DEL/TTC-G/G haplotype carriers (12.49 and 0.09 μmol/l per g/m² , respectively; p < 0.05). Computational predictions suggested that the two polymorphisms overlapped with putative binding sites of several miRNAs.

CONCLUSIONS

The rs3737966 and rs35134728 polymorphisms in MTHFR were associated with serum MTX concentrations. The findings of the present study indicate that miRNAs might be involved in the post-transcriptional regulation of MTHFR.

Association between SLC19A1 Gene Polymorphism and High Dose Methotrexate Toxicity in Childhood Acute Lymphoblastic Leukaemia and Non Hodgkin Malignant Lymphoma: Introducing a Haplotype based Approach

Background

We investigated the clinical relevance of SLC 19A1 genetic variability for high dose methotrexate (HD-MTX) related toxicities in children and adolescents with acute lymphoblastic leukaemia (ALL) and non Hodgkin malignant lymphoma (NHML).

Patients and methods

Eighty-eight children and adolescents with ALL/NHML were investigated for the influence of SLC 19A1 single nucleotide polymorphisms (SNPs) and haplotypes on HD-MTX induced toxicities.

Results

Patients with rs2838958 TT genotype had higher probability for mucositis development as compared to carriers of at least one rs2838958 C allele (OR 0.226 (0.071–0.725), p < 0.009). Haplotype TGTTCCG (H4) statistically significantly reduced the risk for the occurrence of adverse events during treatment with HD-MTX (OR 0.143 (0.023–0.852), p = 0.030).

Conclusions

SLC 19A1 SNP and haplotype analysis could provide additional information in a personalized HD-MTX therapy for children with ALL/NHML in order to achieve better treatment outcome. However further studies are needed to validate the results.

Methotrexate elimination and toxicity: MTHFR 677C>T polymorphism in patients with primary CNS lymphoma treated with high-dose methotrexate

The genetic association of the methylenetetrahydrofolate reductase gene (MTHFR) 677C>T polymorphism with methotrexate (MTX)-associated toxicity has been evaluated and conflicting results have been reported. The substantial heterogeneity of the studied population was suggested to be a possible explanation because ethnicity, MTX dose, coadministered chemotherapeutic agents, and folinate rescue dosage regimen could alter the MTX toxicity profile. The patient population was homogenized by limiting the cancer type to primary central nervous system lymphoma and chemotherapy protocol to a high-dose MTX monotherapy regimen. A total of 111 patients with 402 chemotherapy courses were analyzed. MTHFR 677C>T polymorphism was identified as an independent predictive marker for MTX-associated hematologic toxicity (odds ratio, 2.60; 95% confidence interval, 1.32-5.09; P = .0055). Clinically significant nephrotoxicity occurred in patients without delayed elimination, suggesting roles for factors other than serum MTX levels. MTX-induced hepatotoxicity and oral mucositis occurred independently of plasma MTX levels.

The frequency of hepatotoxicity and myelotoxicity in leukemic children with different high doses of methotrexate

Background and objectives

Methotrexate (MTX) is a chemotherapeutic agent that functions as a folic acid antagonist. The frequency of high dose methotrexate (HDMTX)-associated toxicity is variable. In this study, we investigated the frequency of myelotoxicity and hepatotoxicity 7 days after HDMTX infusion.

Patients and methods

This study included children diagnosed with acute lymphoblastic leukemia (ALL) between January 2010 and April 2015. The patient blood counts and biochemical parameters measured before and after 7 days of HDMTX infusion were retrospectively recorded. We assessed HDMTX infusions for 48 children. The number of patients and drug doses included the following: 17 children receiving 1 g/m² (68 infusions), 14 children receiving 2 g/m² (56 infusions), and 17 children receiving 5 g/m² (68 infusions). The classification of toxicity was made based on the Common Terminology Criteria for Adverse Events (CTCAE) 2010 criteria. Myelotoxicity was defined as a hemoglobin level <10 g/L and absolute neutrophil count <1 × 10⁹/L or platelet count <75 × 10⁹/L. The presence of transaminase levels ≥5 times the upper limit was considered to be hepatotoxicity grade ≥3. The MTX levels at 42 h in patients with and without toxicity were compared to evaluate the correlation between MTX levels, hematologic parameters, and transaminase levels.

Results

Myelotoxicity was observed in 35.2%, 37.5%, and 33.8% of the infusions, and hepatotoxicity grade ≥3 was detected in 13.2%, 12.5%, and 11.7% of the infusions in patients receiving 1, 2 and 5 g/m² HDMTX after 7 days, respectively. There was no statistically significant difference between MTX levels at 42 h in patients with and without toxicity (P > .05, for all). There was no correlation between hematologic parameters and transaminase levels and MTX levels at 42 h.

Conclusion

Hematologic toxicity was the most common toxicity observed. The data indicate the hematologic toxicity increased after repeated cycles in patients receiving 5 g/m². However, the hepatic toxicity decreased with additional cycles. Our results show the level of MTX at 42 h is not effective to identify toxicity.

Pharmacogenomics in Pediatric Oncology: Review of Gene-Drug Associations for Clinical Use

During the 3rd congress of the European Society of Pharmacogenomics and Personalised Therapy (ESPT) in Budapest in 2015, a preliminary meeting was held aimed at establishing a pediatric individualized treatment in oncology and hematology committees. The main purpose was to facilitate the transfer and harmonization of pharmacogenetic testing from research into clinics, to bring together basic and translational research and to educate health professionals throughout Europe. The objective of this review was to provide the attendees of the meeting as well as the larger scientific community an insight into the compiled evidence regarding current pharmacogenomics knowledge in pediatric oncology. This preliminary evaluation will help steer the committee’s work and should give the reader an idea at which stage researchers and clinicians are, in terms of personalizing medicine for children with cancer. From the evidence presented here, future recommendations to achieve this goal will also be suggested.

Association Between Combined Presence of Hepatitis C Virus and Polymorphisms in Different Genes With Toxicities of Methotrexate and 6-Mercaptopurine in Children With Acute Lymphoblastic Leukemia

BACKGROUND

The aim of the present study is to determine the correlation of hepatitis C virus (HCV) infection and polymorphisms in different genes with toxicity of either methotrexate (MTX) or 6-mercaptopurine (6-MP) administered to children with acute lymphoblastic leukemia (ALL).

PROCEDURE

One hundred children with low-risk ALL, who were treated according to the St. Jude Total therapy XV, were recruited. The recruited children were receiving MTX and 6-MP during maintenance phase. Patients were excluded from the study if they had other types of leukemia. Genotyping analyses for the thiopurine methyltransferase (TPMT), methylenetetrahydrofolate reductase (MTHFR), and glutathione S-transferase (GST) genes were performed using a combination of polymerase chain reaction (PCR) and PCR-RFLP (where RFLP is restriction fragment length polymorphism) protocols. Relevant clinical data on adverse drug reactions were collected objectively (blinded to genotypes) from the patient medical records.

RESULTS

There was a significant correlation between the combined presence of HCV and TPMT*3B G460A gene polymorphisms and grades 2-4 hepatotoxicity as aspartate aminotransferase (AST) elevation (P < 0.04). The same observation was seen when comparing either the presence of HCV alone or the presence of the gene polymorphism alone. A significant association between the combined presence of HCV and MTHFR C677T polymorphism and grades 2-4 hepatotoxicity as alanine aminotransferase (ALT), AST, and alkaline phosphatase (ALP) elevation was observed (P values <0.001, 0.02, and 0.001, respectively). The presence of HCV infection had a significant negative effect on hepatic transaminases.

CONCLUSIONS

The present data support a role for combining analysis of genetic variation in drug-metabolizing enzymes and the presence of HCV in the assessment of specific drugs toxicities in multiagent chemotherapeutic treatment regimens.

Influence of genetic polymorphisms in the folate pathway on toxicity after high-dose methotrexate treatment in pediatric osteosarcoma

BACKGROUND

Methotrexate (MTX), one of the main drugs used to treat osteosarcoma, is a representative folic acid antagonist. Polymorphisms of various enzymes involved in the metabolism of MTX could contribute to differences in response to MTX in pediatric osteosarcoma patients.

METHODS

Blood and tissue samples were obtained from 37 pediatric osteosarcoma patients who were treated with high-dose MTX therapy. The following 4 single nucleotide polymorphisms (SNPs) were analyzed: ATIC 347C>G, MTHFR 677C>T, MTHFR 1298A>C and SLC19A1 80G>A. Serial plasma MTX concentrations after high-dose MTX therapy and MTX-induced toxicities were evaluated. Correlations among polymorphisms, MTX concentrations and treatment-induced toxicities were assessed.

RESULTS

Plasma MTX levels at 48 hours after high-dose MTX infusion were significantly associated with SLC19A1 80G>A (P=0.031). Higher plasma levels of MTX at 48 and 72 hours were significantly associated with MTX-induced mucositis (P=0.007 and P=0.046) and renal toxicity (P=0.002), respectively. SNP of SLC19A1 gene was associated with development of severe mucositis (P=0.026).

CONCLUSION

This study suggests that plasma levels of MTX are associated with GI and renal toxicities after high-dose MTX therapy, and genetic polymorphisms that affect the metabolism of MTX may influence drug concentrations and development of significant side effects in pediatric patients treated with high-dose MTX.

Gene polymorphisms in the folate metabolism and their association with MTX-related adverse events in the treatment of ALL

The antifolate drug methotrexate (MTX) is widely used in the treatment of various neoplastic diseases, including acute lymphoblastic leukemia (ALL). MTX significantly increases cure rates and improves patients' prognosis. Despite that it achieved remarkable clinical success, a large number of patients still suffer from treatment toxicities or side effects. Even to this date, chemotherapeutic regiments have not been personalized because of interindividual differences that affect MTX response, especially polymorphisms in key genes. The pharmacological pathway of MTX in cells is useful to identify gene polymorphisms that influence the process of treatment. The aim of this review was to discuss the gene polymorphisms of drug-metabolizing enzymes in the MTX pathway and their toxicities on ALL treatment.

Risk analysis, diagnosis and management of gastrointestinal mucositis in pediatric cancer patients

Mucositis is a complex inflammatory reaction of the mucous membranes of the alimentary tract upon chemotherapy and radiotherapy treatment in oncology patients. Mucositis can be subdivided in oral and gastrointestinal mucositis (GI mucositis). The damage to the gastrointestinal tract compromises the intestinal function and thereby the nutritional status and the quality of life, and eventually affects survival. The literature on GI mucositis focuses mainly on adults. This review focuses on data available on GI mucositis in pediatric cancer patients. An evaluation of the clinical presentation and consequences of GI mucositis in children is outlined. The review summarizes key issues for clinicians with respect to risk analysis for developing mucositis and the diagnosis of this condition in children. Information on these issues is obtained from clinical trials in children and adults, and from animal models. Diagnostic tools and assessment of severity of GI mucositis in children is elaborated on. Furthermore, the clinical management of the symptoms and consequences of GI mucositis in children, with specific focus on nutritional support, are discussed.

Genetic and metabolic determinants of methotrexate-induced mucositis in pediatric acute lymphoblastic leukemia

Methotrexate (MTX) is an effective and toxic chemotherapeutic drug in the treatment of pediatric acute lymphoblastic leukemia(ALL). In this prospective study, we aimed to identify metabolic and genetic determinants of MTX toxicity. One hundred and thirty-four Dutch pediatric ALL patients were treated with four high infusions MTX (HD-MTX: 5 g m(-2)) every other week according to the DCOG-ALL-10 protocol. Mucositis (National Cancer Institute grade ⩾ 3) was the most frequent occurring toxicity during the HD-MTX phase (20%) and occurred especially after the first MTX course. Mucositis was not associated with plasma MTX, plasma folate or plasma homocysteine levels. Patients with mucositis had higher erythrocyte folate levels at the start of protocol M than patients without mucositis (median 1.4 vs 1.2 μmol l(-1), P<0.008), this could reflect an increased MTX uptake in mucosal cells of patients with mucositis. From 17 single-nucleotide polymorphisms in the MTX pathway, only patients with the wild-type variant of rs7317112 SNP in the ABCC4 gene had more mucositis (AA (39%) vs AG/GG (15%), P=0.016). We found no evidence that erythrocyte folate levels mediate in the association between the rs7317112 and mucositis.

Effect of polymorphisms within methotrexate pathway genes on methotrexate toxicity and plasma levels in adults with hematological malignancies

Aim: Pharmacogenetics of methotrexate (MTX) contributes to interindividual differences in toxicity. We aimed to evaluate the impact of SNPs within the MTX pathway genes on MTX-induced toxicity and MTX plasma levels at 48 h following treatment in Asian adults with acute lymphoblastic leukemia or non-Hodgkin lymphoma. Patients & methods: Patients (n = 71) were genotyped for MTHFR C677T, MTHFR A1298C, SLC19A1 G80A, ABCG2 C421A and ABCB1 C3435T using the Sequenom MassARRAY® platform. Plasma MTX concentrations at 48 h were measured by fluorescence polarization immunoassay. Results: Forty-eight patients had hematopoietic toxicity, 51 had hepatic toxicity and 36 had mucositis. Patients homozygous for MTHFR 677TT were associated with increased risk of both hematopoietic (odds ratio [OR]: 9.03; 95% CI: 2.28–36.16; p = 0.002) and hepatic (OR: 3.92; 95% CI: 1.01–15.11; p = 0.036) toxicities. Hepatic toxicity was associated with SLC19A1 G80A (OR: 5.27, 95% CI: 1.21–22.72; p = 0.032) and ABCB1 C3435T (OR: 8.62; 95% CI: 1.96–37.57; p = 0.004). However, polymorphisms in MTHFR A1298C and ABCG2 C421A were not associated with any of the toxicities, and mucositis was not associated with any polymorphisms of the MTX pathway genes. Patients with MTHFR C677T and ABCB1 C3435T polymorphisms appear to have significantly higher MTX plasma concentrations (p < 0.05). Conclusion: Our results in Asian adults provides evidence for the contribution pharmacogenetics to the toxicity of high-dose MTX and plasma MTX concentrations at 48 h following treatment in patients with acute lymphoblastic leukemia or non-Hodgkin lymphoma. These results will contribute towards the effort of MTX therapy individualization.

Original submitted 24 April 2014; Revision submitted 6 June 2014

Pharmacogenetics of childhood acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) is the major pediatric cancer in developed countries. Although treatment outcome has improved owing to advances in chemotherapy, there is still a group of patients for which therapy fails while some patients experience severe toxicity. In the last few years, several pharmacogenetic studies have been performed to search for markers of outcome and toxicity in pediatric ALL. However, to date, TPMT is the only pharmacogenetic marker in ALL with clinical guidelines for drug dosing. In this article, we will provide an overview of the most important findings carried out in pharmacogenetics for pediatric ALL, such as the interest drawn by methotrexate transporters in the context of methotrexate treatment. Even if most of the studies are centered on coding genes, we will also point to new approaches focusing on noncoding regions and epigenetic variation that could be interesting for consideration in the near future.

Association between reduced folate carrier G80A polymorphism and methotrexate toxicity in childhood acute lymphoblastic leukemia: a meta-analysis

Abstract Methotrexate (MTX) is a key component of chemotherapeutic regimens for childhood acute lymphoblastic leukemia (ALL), and enters the cell via active transport mediated by the reduced folate carrier (RFC1). A major single-nucleotide polymorphism of the RFC1 gene, G80A, which affects the activity of RFC1, may influence MTX toxicity in pediatric ALL. We collected all studies that investigated the association of RFC1 G80A polymorphism and MTX toxicity in pediatric ALL, and found inconsistency among their results. The aim of this meta-analysis was to summarize all of these studies in order to clarify the correlation between the RFC1 G80A polymorphism and MTX toxicity in pediatric ALL. A recessive model demonstrated no influence of the RFC1 G80A genotype on MTX toxicity. In conclusion, the RFC1 G80A polymorphism does not seem to be a good marker of MTX-related toxicity in pediatric ALL.

Uptake carriers and oncology drug safety

Members of the solute carrier (SLC) family of transporters are responsible for the cellular influx of a broad range of endogenous compounds and xenobiotics in multiple tissues. Many of these transporters are highly expressed in the gastrointestinal tract, liver, and kidney and are considered to be of particular importance in governing drug absorption, elimination, and cellular sensitivity of specific organs to a wide variety of oncology drugs. Although the majority of studies on the interaction of oncology drugs with SLC have been restricted to the use of exploratory in vitro model systems, emerging evidence suggests that several SLCs, including OCT2 and OATP1B1, contribute to clinically important phenotypes associated with those agents. Recent literature has indicated that modulation of SLC activity may result in drug-drug interactions, and genetic polymorphisms in SLC genes have been described that can affect the handling of substrates. Alteration of SLC function by either of these mechanisms has been demonstrated to contribute to interindividual variability in the pharmacokinetics and toxicity associated with several oncology drugs. In this report, we provide an update on this rapidly emerging field.

Pharmacogenetics of methotrexate in acute lymphoblastic leukaemia: why still at the bench level?

PURPOSE

The antifolate drug methotrexate (MTX) was introduced into clinical practice about 60 years ago and remains an important component of different acute lymphoblastic leukemia (ALL) treatment protocols. It acts by inhibiting several enzymes in the folate pathway, thereby resulting in the disruption of folate homeostasis. To date, treatment regimens have not been personalized despite there being experimental evidence that gene polymorphisms of folate metabolizing enzymes affect MTX response. The aim of this review was to evaluate the influence of genetic polymorphisms of the enzymes involved in the MTX pathway on ALL treatment outcomes and identify factors underlining the failure to personalize MTX therapy.

METHODS

We conducted a literature search in PUBMED and Google Scholar using the following key words: methotrexate, polymorphism, acute lymphoblastic leukemia, pharmacogenetics, pharmacogenomics and personalized medicine.

RESULTS

The reasons for the failure to personalize MTX therapy may be due to (1) most studies involving single-center, small-sized cohorts, (2) differences in MTX dose across different protocols, (3) failure to consider minimal residual disease as a risk factor for post-induction treatment, (4) differences in outcome criteria between studies and (5) failure to consider the folate levels of a patient before initiation of MTX therapy. Although high-throughput techniques allow the mapping of thousands of genetic polymorphisms in a single run, it remains a major challenge to dissect out folate-metabolizing enzymes which have a high impact on the efficacy and toxicity of MTX and which, therefore, could be the targets for intervention.

CONCLUSIONS

Prospective pharmacogenetic studies which consider all of the above-mentioned factors should be undertaken to facilitate the design of personalized MTX treatment for ALL patients.

Polymorphisms of MTHFR Associated with Higher Relapse/Death Ratio and Delayed Weekly MTX Administration in Pediatric Lymphoid Malignancies

Backgrounds. Outcome of childhood malignancy has been improved mostly due to the advances in diagnostic techniques and treatment strategies. While methotrexate (MTX) related polymorphisms have been under investigation in childhood malignancies, many controversial results have been offered. Objectives. To evaluate associations of polymorphisms related MTX metabolisms and clinical course in childhood lymphoid malignancies. Method. Eighty-two acute lymphoblastic leukemia and 21 non-Hodgkin's lymphoma children were enrolled in this study. Four single nucleotide polymorphisms in 2 genes (MTHFR (rs1801133/c.677C>T/p.Ala222Val and rs1801131/c.1298A>C/p.Glu429Ala) and SLCO1B1 (rs4149056/c.521T>C/p.V174A and rs11045879/c.1865+4846T>C)) were genotyped by Taqman PCR method or direct sequencing. Clinical courses were reviewed retrospectively. Results. No patient who had the AC/CC genotype of rs1801131 (MTHFR) had relapsed or died, in which distribution was statistically different among the AA genotype of rs1801131 (P = 0.004). Polymorphisms of SLCO1B1 (rs11045879 and rs4149056) were not correlated with MTX concentrations, adverse events, or disease outcome. Conclusions. Polymorphisms of MTHFR (rs1801131) could be the plausive candidate for prognostic predictor in childhood lymphoid malignancies.

Cancer pharmacogenomics in children: research initiatives and progress to date

Over the last few decades, cure rates for pediatric cancer have increased dramatically, and now over 80 % of children with cancer are cured of their disease. This improvement in cure has come with a significant cost, with many children suffering irreversible, life-threatening, or long-lasting toxicities due to the medications required during their treatment. In the last 2 decades, major technological advances in genomics and the mapping of the human genome have made it possible to identify genetic differences between children in order to investigate differing responses to cancer therapy and to help explain why children treated with the same medications can have different outcomes. The emerging field of pharmacogenomics has had many important findings in pediatric cancer. The focus of this review is drug toxicity in pediatric cancer and the use of pharmacogenomics to reduce these adverse drug reactions, with a specific focus on thiopurines, methotrexate, cisplatin, vincristine and anthracyclines. Future areas of research and the need for international collaboration are discussed.

Impact of genetic polymorphisms on chemotherapy toxicity in childhood acute lymphoblastic leukemia

The efficacy of chemotherapy in pediatric acute lymphoblastic leukemia (ALL) patients has significantly increased in the last 20 years; as a result, the focus of research is slowly shifting from trying to increase survival rates to reduce chemotherapy-related toxicity. At the present time, the cornerstone of therapy for ALL is still formed by a reduced number of drugs with a highly toxic profile. In recent years, a number of genetic polymorphisms have been identified that can play a significant role in modifying the pharmacokinetics and pharmacodynamics of these drugs. The best example is that of the TPMT gene, whose genotyping is being incorporated to clinical practice in order to individualize doses of mercaptopurine. However, there are additional genes that are relevant for the metabolism, activity, and/or transport of other chemotherapy drugs that are widely use in ALL, such as methotrexate, cyclophosphamide, vincristine, L-asparaginase, etoposide, cytarabine, or cytotoxic antibiotics. These genes can also be affected by genetic alterations that could therefore have clinical consequences. In this review we will discuss recent data on this field, with special focus on those polymorphisms that could be used in clinical practice to tailor chemotherapy for ALL in order to reduce the occurrence of serious adverse effects.

A systematic review and meta-analysis of MTHFR polymorphisms in methotrexate toxicity prediction in pediatric acute lymphoblastic leukemia

Methotrexate (MTX) is an important component of therapy used to treat childhood acute lymphoblastic leukemia (ALL). Two single-nucleotide polymorphisms (SNPs) in the methylenetetrahydrofolate reductase (MTHFR) gene, C677T and A1298C, affect MTHFR activity. A large body of studies has investigated the potential role of MTHFR SNPs in MTX toxicity in pediatric ALL. However, the results are controversial. In this review and meta-analysis, we critically evaluate the relationship between the C677T and A1298C polymorphisms of MTHFR and MTX toxicity in pediatric ALL. The majority of published reports do not find associations between MTHFR polymorphisms and toxicity in pediatric ALL. When associations are reported, often the results are contradictory to each other. The meta-analysis confirms a lack of association. In conclusion, MTHFR, C677T and A1298C polymorphisms do not seem to be good markers of MTX-related toxicity in pediatric ALL.

Pharmacokinetic and pharmacogenetic determinants and considerations in chemotherapy selection and dosing in infants

INTRODUCTION

There is a lack of high-quality data regarding optimal chemotherapy dosage regimens among infants. Dosing regimens for chemotherapy during the first year of life are commonly based on empiric recommendations extrapolated from older children; however, balancing efficacy and toxicity is critical as severe adverse drug reactions may lead to treatment failure or reduced adherence to needed medications.

AREAS COVERED

This review describes pharmacokinetic and pharmacogenetic considerations when administering chemotherapeutic agents to infants. Examples of commonly used agents are provided with practical recommendations for dosing adjustments.

EXPERT OPINION

Optimal chemotherapy for children and infants in particular has lagged behind the remarkable progress in cancer treatment and it is clear that far more basic and clinical research are needed with respect to the mechanistic basis of age-dependent differences in pharmacokinetic parameters. More recent studies which have combined pharmacokinetic data with clinical toxicity and outcome data have resulted in a number of more evidence-based guidelines at least for the initial chemotherapy dosing; however, at present, the dosing of chemotherapy drugs in neonates and infants remains largely empiric.

Influence of folate pathway polymorphisms on high-dose methotrexate-related toxicity and survival in childhood acute lymphoblastic leukemia

The prediction of high-dose methotrexate (HD-MTX) toxicity is a key issue in the individualization of treatment in childhood acute lymphoblastic leukemia (ALL). Our aim was to evaluate the influence of MTX pathway polymorphisms on HD-MTX treatment outcome in children with ALL. In total, 167 children with ALL were genotyped for methylenetetrahydrofolate dehydrogenase (MTHFD1) 1958G > A, methylenetetrahydrofolate reductase (MTHFR) 677C > T and 1298A > C and thymidylate synthase (TYMS) 2R > 3R polymorphisms. The MTHFD1 1958A allele significantly reduced the odds of hepatotoxicity (adjusted p = 0.009), while the TYMS 3R allele significantly reduced the odds of leukocytopenia and thrombocytopenia (adjusted p = 0.005 and adjusted p = 0.002, respectively). MTHFR polymorphisms did not influence HD-MTX-related toxicity, but a significant effect of MTHFR 677C > T-TYMS 2R > 3R and MTHFD1 1958G > A-MTHFR 677C > T interactions on HD-MTX-related toxicity was observed. None of the investigated polymorphisms influenced survival. Our study suggests an important role of polymorphisms and gene-gene interactions within the folate pathway in HD-MTX-related toxicity in childhood ALL.

The role of MTHFR and RFC1 polymorphisms on toxicity and outcome of adult patients with hematological malignancies treated with high-dose methotrexate followed by leucovorin rescue

PURPOSE

In the last years, the influence of different genes involved in metabolism of chemotherapeutic agents has been studied. Methotrexate (MTX) is a key compound of chemotherapeutic regimens used in the treatment of acute lymphoblastic leukemia (ALL), primary central nervous system lymphoma (PCNSL) and Burkitt's lymphomas (BL). This study aims to evaluate the role of MTHFR C677T and A1298C polymorphisms and G80A reduced folate carrier gene (RFC1) in a cohort of adult patients with lymphoproliferative malignancies submitted to high-dose MTX followed by leucovorin rescue.

METHODS

We performed the analysis of these polymorphisms on genomic DNA with RFLP-PCR.

RESULTS

Patients carrying MTHFR A1298C variant showed decreased hepatic and hematological toxicity (P = 0.03). Overall survival (OS) and progression-free survival (PFS) between homozygous wild-type and variant patients for the RFC1 G(80)A were significantly different (P = 0.035 and P = 0.02, respectively). A significant correlation between hematological toxicity and age (P = 0.003) was observed. There was no significant influence of MTHFR C677T genotype on toxicity, OS and PFS.

CONCLUSIONS

Leucovorin rescue given after high-dose MTX probably accounts for the lack of influence of C677T polymorphism. To better define a role of RFC1 polymorphism on patients outcome, it would be worthwhile to perform a study on intracellular MTX level and RFC1 substrate binding affinities in different genotypes.

Polymorphisms of the SLCO1B1 gene predict methotrexate-related toxicity in childhood acute lymphoblastic leukemia

BACKGROUND

Methotrexate (MTX) is an important component of the therapy for childhood acute lymphoblastic leukemia. Treatment with high-dose MTX often causes toxicity, recommending a dose reduction and/or cessation of treatment. Polymorphisms in genes involved in the MTX metabolism have been associated with toxicity with controversial results. The discrepancies could be due to differences in treatment protocols among studies, small, or non-homogeneous populations or the use of different toxicity criteria. The aim of the present study was to analyze the possible correlation of polymorphisms of genes involved in the MTX metabolism with the toxicity during therapy with the well-established LAL/SHOP protocol.

PROCEDURE

We analyzed 10 polymorphisms in seven genes (MTHFR, TS, SHMT1, RFC1, ABCB1, ABCG2, and SLCO1B1) from the MTX metabolism in 115 Spanish pediatric B-ALL patients, using MTX plasma concentration as an objective and quantifiable marker of toxicity.

RESULTS

We confirmed the suitability of MTX plasma levels as a toxicity marker. We found a statistically significant association between MTX plasma concentration and the SLCO1B1 rs11045879 CC genotype (P = 0.030). The rs4149081 AA genotype, in the same gene, could also be an indicator for high-MTX plasma concentrations. We did not find any significant association in the other genetic polymorphisms analyzed.

CONCLUSIONS

Identification of the rs4149081 and rs11045879 SLCO1B1 polymorphisms in children with ALL could be a useful tool for monitoring patients at risk of low-MTX clearance in order to avoid MTX-related toxicity.