Factors influencing delayed high-dose methotrexate excretion and its correlation with adverse reactions after treatment in children with malignant hematological tumors

Introduction

Methotrexate (MTX), a common anticancer medication, works by inhibiting dihydrofolate reductase to prevent dihydrofolate from being converted to physiologically active tetrahydrofolate, thus obviating DNA biosynthesis. Clinical terminology refers to an MTX dose of 500 mg/m² as high-dose MTX (HDMTX). This dosage is frequently used to treat malignant hematologic neoplastic disorders such osteosarcoma, non-Hodgkin lymphoma, and acute lymphoblastic leukemia, among others (1). Unless the toxic effects of MTX are terminated by repeated calcium folinate (CF) injections over a sustained period of 2–3 days, vigorous rehydration and urinary alkalinization before and after therapy are also required. Infusion of HDMTX alone for 4–36 hours may be fatal. Even with the aforementioned precautions, a small percentage of patients nevertheless experience delayed MTX excretion, which leads to severe negative effects, such as acute liver and kidney injury, bone marrow suppression, mucositis, gastrointestinal problems, fever, and infection (2). Blood concentrations of >1 µmol/L at 48 hours and >0.1 µmol/L at 72 hours following injection are considered to indicate delayed MTX excretion (3).

According to research, the medication dose, body surface area dose, and patient age are the main variables that affect the delayed excretion of HDMTX in adults (4). Additionally, while receiving HDMTX treatment, patients may concurrently receive proton pump inhibitors (5,6), nonsteroidal anti-inflammatory drugs (NSAIDs) (7), and penicillin medication (8), which may alter how well MTX is cleared from the body. The Chinese Guidelines for the evidence-based use of HDMTX recommends clinical monitoring of blood concentrations and adjustment of the administered dose of the patient’s next cycle of chemotherapy based on the patient’s situation, including results of therapeutic efficacy, drug tolerance, and therapeutic drug monitoring (9). Further clinical research is required to identify the variables affecting children’s blood levels because of their distinct physiology and high growth rates, which can result in different pharmacokinetics from adults. By preventing and controlling disease, preventive medicine seeks to improve patients’ overall health. For better malignant tumor prevention, treatment, and progression control, it is especially crucial to increase public health awareness and popularize knowledge concerning malignant tumors (10).

This study thus aimed to offer a theoretical foundation for the clinical prevention of delayed HDMTX excretion in children by retrospectively analyzing the influencing factors of delayed MTX excretion and the occurrence of adverse events in pediatric patients. We further sought to identify the risk factors during HDMTX treatment in children and to recommend preventive medical approaches to lower the likelihood of adverse reactions related to excretion delay by examining the relationship between excretion delay and adverse responses in children. This study’s findings may bear significant clinical ramifications for preventing HDMTX excretion delay and its associated side effects. We present this article in accordance with the STROBE reporting checklist (available at https://tp.amegroups.com/article/view/10.21037/tp-23-615/rc).

Methods

Ethics

This retrospective single-center clinical study was conducted at Shanghai Children’s Medical Center, Shanghai, China. This study was conducted in accordance with the Declaration of Helsinki (as revised in 2013). This research was approved by the Institutional Review Board of Shanghai Children’s Medical Center Affiliated with Shanghai Jiao Tong University School of Medicine (No. SCMCIRB-K2023177-1) and individual consent for this retrospective analysis was waived.

Participants

Children who underwent HDMTX chemotherapy in the Department of Hematology and Oncology of Shanghai Children’s Medical Center from April 2021 to October 2021 were selected, and their blood drug concentration was measured. All the children were free of infection, and their blood, liver, and kidney function met the standard of chemotherapy when they were treated with HDMTX. Children who received HDMTX via a 24-hour drip and had their CF stabilized at less than 0.3 µmol/L (Shanghai Children’s Medical Center’s lower limit of measurement) met the inclusion criteria. Children whose MTX blood content was not brought down to 0.3 µmol/L and those whose MTX concentration data during HDMTX treatment were lacking were excluded.

Research methods

Treatment regimen

HDMTX (2–5 g/m²) was dissolved in 0.9% sodium chloride injection or 5% dextrose injection; patients first received a loading dose of 1/10 of the total amount, which was rapidly infused intravenously over 0.5 hours, and the remaining dose was infused intravenously at an even rate over 23.5 hours. After 42 hours had passed since the first administration of MTX, CF was administered at a dose of 15 mg/m² q6h until the MTX concentration was <0.3 µmol/L (11). At least 12 hours before the delivery of HDMTX, monitoring of hydration, urine alkalinization, and maintenance of urine pH in the range of 7.0–8.0 was initiated. The patient’s individual chemotherapy regimen was used to determine the appropriate relief treatment if delayed MTX excretion occurred according to the Chinese Children’s Cancer Group study mature B non-Hodgkin lymphoma study plan 2015 (CCCG-BNHL-2015) and the Chinese Children’s Cancer Group study acute lymphoblastic leukemia study plan 2020 (CCCG-ALL-2020). In this study, MTX 44th hour blood-drug concentration C_44h >1.0 µmol/L and C_68h >0.3 µmol/L were used as the criteria for delayed excretion.

Detection method for blood-drug concentration

The serum MTX concentration was assessed using a Viva-E drug concentration analyzer (Siemens Healthineers, Munic, Germany) with enzyme-expanded immunoassay 20 hours after the end of the MTX infusion and then every 24 hours continuously until the blood-drug concentration was <0.3 µmol/L.

Adverse reactions

During chemotherapy and 3 weeks after it had ended, data on the biochemical indicators of blood routine (white blood cell count, neutrophil count, hemoglobin, platelet count), liver and kidney function, and the adverse responses in the children receiving the chemotherapy were gathered. The Common Terminology Criteria for Adverse Events (CTCEA) version 5.0 were used to evaluate adverse events (12). Fever was defined in this study as a child’s axillary temperature exceeding 37 °C, oral temperature exceeding 37.3 °C, and rectal temperature exceeding 37.6 °C; infection was defined as the occurrence of fever following chemotherapy or the emergence of obvious clinical symptoms, such as a cough or runny nose, or the presence of clearly visible evidence of pneumonia or liver abscess on imaging; a neutrophil count <0.5×10⁹/L was defined as grade 4 myelosuppression; hepatic function impairment injury was defined as aspartate transaminase (AST) or alanine aminotransferase (ALT) enzyme values three times higher than the upper limit of normal; and acute kidney injury was defined as a rise in creatinine level of more than 50% the baseline value.

Combination medication

Drugs that could potentially be associated with delayed MTX excretion, such as chemotherapy drugs, antiemetics, and other medications, but not topical treatments, were coadministered with MTX before and after the child underwent HDMTX treatment.

Statistical methods

The proportion of missing nonlaboratory was less than 1%. Missing observations were excluded from the analysis. SPSS 27.0 (IBM Corp., Armonk, New York, USA) was used for the statistical analysis of data. The demographic data of children with normal distribution and laboratory indicators are expressed as the mean ± standard deviation (SD). The incidence of adverse reactions was tested by Chi-squared test, and logistic regression was used for the analysis of the delayed excretion of HDMTX and the single and multivariate factors leading to infections in the children. At a P value <0.05, a difference was deemed statistically significant.

Results

Delayed excretion in children

In this study, a total of 99 children who underwent HDMTX chemotherapy and who undergone blood concentration tests were included. The average age was 6.76 (range, 1.08–15.17) years. There were 34 girls (34.3%) and 65 boys (65.7%) enrolled in the study. The most common diagnosis was acute lymphoblastic leukemia (53.8% of patients), followed by lymphoma (42.2%). Of the 199 sessions of HDMTX chemotherapy, 40 involved MTX delayed excretion, with an incidence of 20.1%.

One-way analysis of delayed HDMTX excretion

In terms of gender and concurrent drug administration, one-way logistic regression analysis revealed no statistically significant differences between children in the non-delayed excretion group and the delayed excretion group (P>0.05), but there were statistically significant differences in age, body surface area, MTX concentration at 24 hours, and MTX dosage with delayed excretion of HDMTX (P<0.05). In the 199 sessions of HDMTX chemotherapy, age ≥9 years old, body surface area ≥1 m², body surface area dose ≥4 g/m², and MTX concentration ≥64 µmol/L at 24 hours were associated with a higher incidence of MTX excretion delay (Table 1).

Multivariate analysis of HDMTX excretion delay

Factors that were statistically significant in the univariate analysis were included in the multivariate logistic regression analysis using the forward stepwise method, and the results showed that age ≥9 years and MTX concentration ≥64 µmol/L at 24 hours were independent risk factors for delayed MTX excretion (P<0.05) (Table 2).

Effect of HDMTX excretion delay on adverse reactions

During 199 HDMTX chemotherapy sessions, 43.7% of the children experienced fever (within the 3-week observation window afterward), 46.7% infection, 53.3% myelosuppression, 26.6% mucositis, 19.1% gastrointestinal problems, 4.0% acute kidney injury, and 15.0% abnormal liver function as side effects. Children with excretion delay were significantly more likely than children with normal excretion to experience fever, infection, mucositis, gastrointestinal symptoms (vomiting, nausea, abdominal discomfort), or reduced platelet count. The probability of other types of adverse events was not significantly impacted by delayed MTX excretion (Table 3).

Univariate analysis of the effect of HDMTX excretion delay on infection

Univariate analysis revealed that delayed excretion of MTX, drug dosage, body surface area dosage, MTX concentration at the 24 and 44 hours, granulocyte deficiency, leukocyte decrease, hemoglobin decrease, platelet decrease, and the combination of medications including prednisone, iso-cyclophosphamide, etoposide, vinblastine, mercaptopurine, and rituximab, pembrolizumab were among the factors associated with the emergence of infection in children following the administration of HDMTX (P<0.05) (Table 4).

Multivariate analysis of the effect of delayed HDMTX excretion on infection

The results of the multivariate logistic regression analysis in the forward stepwise regression analysis revealed that delayed MTX excretion, decreased leukocyte count, a hemoglobin level <65 g/L, and etoposide intake were independent risk factors for postchemotherapy infection in children (P<0.05) (Table 5). These factors were also found to be statistically significant in the univariate analysis.

Discussion

Despite HDMTX being used to treat a variety of malignant tumors for more than 50 years, its delayed excretion is still not completely understood. MTX-related toxicities are more common in courses with MTX excretion delay (13). In this retrospective, single-center study, an analysis of 199 HDMTX sessions revealed a 20.1% incidence of delayed MTX excretion. Age ≥9 years and MTX concentration ≥64 µmol/L at 24 hours were independent risk factors for delayed MTX excretion, while delayed MTX excretion, reduced leukocyte count, a hemoglobin level <65 g/L, and concurrent use of etoposide were independent risk factors for infection. Additionally, compared to children with normal excretion, children with delayed excretion were more likely to experience negative side effects of fever, infection, mucositis, gastrointestinal problems, and decreased platelet count.

A number of retrospective investigations have been conducted on the factors influencing the delayed excretion of HDMTX, and the prevalence of delayed HDMTX excretion reported in these studies ranges from 7.8% to 19.8% (14-16). Among the 199 chemotherapy sessions in our study, even when the conventional treatments of CF rescue (performed 42 hours after MTX initiation), hydration, and alkalinization (performed 12 hours before MTX initiation) were administered, the incidence of delayed MTX excretion was 20.1%. This outcome was comparable to that of the study by Xu et al. (14) (19.8%), with the exception that the CF rescue in their study began 6 hours earlier than it did in ours—which may be the reason for its somewhat lower frequency of delayed excretion—and at 36 hours following MTX administration. In contrast, the study by Li et al. reported an incidence of delayed MTX excretion of 13.67% (15), which may be related to the fact that hydration was advanced by 1 day (3 L/m² of hydration) and continued for 4 days, with 5% sodium bicarbonate (5 mL/kg) used to alkalinize the urine on the day of chemotherapy for 3 days. In the study by Xu et al., 12.1% of children who were administered MTX experienced excretion delay. This finding may be related to the fact that CF rescue was initiated 36 hours after MTX medication administration, urine was alkalinized 3 days prior to medication administration, and the urine was heavily hydrated and alkalinized for 3 days following MTX’s use (16). A recent small-sample study conducted outside of China found that the incidence of delayed MTX excretion was only 7.8%, which may be due to the study’s sample size and high hydration levels (>3 L/m²) (17). According to the Chinese guidelines for the evidence-based use of HDMTX, intravenous hydration (2.5–3 L/m² for ≥72 hours) should begin 12 hours or earlier before HDMTX infusion, and the MTX concentration in blood should be tested at least once at 24, 48, and 72 hours after the start of titration until the MTX blood concentration is ≤0.1–0.2 µmol/L. The monitoring interval should be shortened and the monitoring frequency should be increased in cases of delayed excretion, acute renal damage, or other major adverse effects, but there is no specific requirement for the increase in frequency, and the concentration test can be increased according to the actual clinical situation. For the 24-hour continuous titration program, it is advised that the first dose of CF be given for relief 36–44 hours after the start of the titration, and when major adverse effects occur, the timing of the initial dose of relief should be altered according to the clinical situation and on an individual basis (9).

In this investigation, the effects of patient variables on the delayed excretion of HDMTX, such as the age of the child and body surface area, were independent risk factors for delayed MTX excretion, which is consistent with Li et al.’s findings (18). According to a study, younger children have a higher MTX clearance than do older children, indicating that MTX clearance declines with age (19). In our study, logistic regression analysis indicated that advanced age was a risk factor for delayed MTX clearance, with children aged ≥9 years having a larger chance of delayed clearance. Early management may lower the frequency of delayed MTX excretion and make HDMTX therapy safer and more effective. As a result, older children should drink more fluids and be more stringently monitored in terms of therapeutic agents.

We discovered a strong correlation between the MTX concentration at the 24 hours and the delayed excretion of MTX in children. The MTX concentration at the 24 hours should, according to the Chinese guidelines for evidence-based use of HDMXT, be between 16 and 40 µmol/L (9). In children, MTX with a C_24h >16 µmol/L can improve clinical efficacy, whereas MTX with a C_24h >40 µmol/L may raise the risk of drug toxicity (3). Therefore, the guidelines suggest 16 and 40 µmol/L as the lower and upper limits of MTX concentration at the 24 hours in children with acute lymphoblastic leukemia, respectively, according to efficacy and safety concerns. Our multivariate analysis showed that a 24-hour MTX concentration >64 µmol/L was associated with delayed excretion. A study has been conducted on reducing the incidence of high 24-hour MTX concentrations via the detection of MTX concentrations at 2, 6, and 8 hours into the HDMTX chemotherapy course, which may help to adjust the drug dose in time (20). No delay in HDMTX excretion caused by the medication combination was encountered in this investigation (P>0.05). According to other research, concurrent proton pump inhibitors and HDMTX increase the blood concentration of MTX, which in turn increases the likelihood of delayed excretion (5). In our study, proton pump inhibitor utilization was also higher in children in the delayed excretion group (12.5% vs. 4.4%), but there was no statistically significant difference (P=0.066), which may be due to the rarity of pediatric proton pump inhibitor combination use, and thus this potential correlation needs to be confirmed by a clinical study with a larger sample size.

During the course of 199 HDMTX chemotherapy sessions examined in our study, the children experienced a range of systemic adverse events, including mucositis, myelosuppression, infection, gastrointestinal problems, hepatic impairment, and renal impairment. In comparison to the non-delayed group, the delayed group had a higher incidence of adverse responses. Children with delayed excretion were significantly more likely to experience fever, infection, mucositis, gastrointestinal symptoms, and platelet count decrease than were children with normal excretion. It has been reported that the occurrence of negative effects and MTX blood concentration are closely connected. Neutropenia, hemoglobin, and thrombocytopenia are frequent clinical signs of hematopoietic poisoning. Myelosuppression in children was discovered to be the most common adverse reaction in this study, which is consistent with other research (21). Infection frequency is increased by granulocyte shortage, and mucosal injury with MTX increases the likelihood of oral infections and perianal abscesses. According to Jiang et al.’s findings, children who experience delayed MTX excretion are more likely to experience gastrointestinal side effects, such as vomiting, nausea, and abdominal discomfort (P<0.001) (22). Children should maintain good oral hygiene, and if grade III or IV oral ulcers develop, oral hypothermia can be administered based on standard care. The frequency of oral mucositis and ulcers in the delayed excretion group (47.5%) was higher than that in the normal excretion group (21.4%), and the difference was statistically significant (P=0.001).

Infection is a common and serious postchemotherapy adverse effect that can be fatal. The results of this study showed that in addition to the common infection susceptibility factors, such as delayed MTX excretion, leukopenia, and hemoglobin <65 g/L, the combination of other antitumor drugs including etoposide, cyclophosphamide, vincristine, and rituximab is a risk factor for infection in children. Etoposide and HDMTX are frequently used in our facility’s treatment of young patients with CCCG-BNHL-2015 (MTX 5 g/m² d1 + etoposide 100 mg/m² d3–5 + vincristine 3 mg/m² d1 + isocyclophosphamide 1,200 mg/m² d1–5 + prednisone 60 mg/m² d1–7). Children with lymphomas on this regimen have a higher risk of infection because the chemotherapy intensity is higher than that in consolidation therapy for children with CCCG-ALL-2020 (MTX 3–5 g/m² + mercaptopurine 25 mg/m²/day).

Limitations

This is a retrospective study and the number of cases was limited. There is still uncertainty as to whether combined use of certain drugs causes delayed excretion. In addition, this study is a single-center study, and the results have some limitations. Therefore, a multi-center prospective study can be conducted in the future, and a relatively balanced control group study can be set up.

Conclusions

In conclusion, there are numerous types adverse reactions associated with HDMTX treatment for hematological malignancies in children. Over the course of chemotherapy, MTX concentration should be monitored over time, and the subsequent treatment plan for children should be adjusted according to the blood concentration so as to effectively reduce the occurrence of adverse reactions and effectively control infection. In addition, it is necessary to strengthen nursing support for children during HDMTX treatment, and actively managing adverse reactions such as vomiting and diarrhea can also substantially contribute to the prevention of delayed MTX excretion.

Acknowledgments

Funding: This article was supported by Hainan Health Science and Technology Innovation Joint Project (No. SQ2023WSJK0179) and Special Science and Technology Plan Project of Universities and Medical Special Science and Technology Plan Project of Universities and Medical Institutions in Sanya City (Nos. 2021GXYL32 and 2021GXYL42).

Footnote

Reporting Checklist: The authors have completed the STROBE reporting checklist. Available at https://tp.amegroups.com/article/view/10.21037/tp-23-615/rc

Data Sharing Statement: Available at https://tp.amegroups.com/article/view/10.21037/tp-23-615/dss

Peer Review File: Available at https://tp.amegroups.com/article/view/10.21037/tp-23-615/prf

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://tp.amegroups.com/article/view/10.21037/tp-23-615/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki (as revised in 2013). The study was approved by the Institutional Review Board of Shanghai Children’s Medical Center Affiliated with Shanghai Jiao Tong University School of Medicine (No. SCMCIRB-K2023177-1) and individual consent for this retrospective analysis was waived.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

References

1. Mahadeo KM, Santizo R, Baker L, et al. Ambulatory high-dose methotrexate administration among pediatric osteosarcoma patients in an urban, underserved setting is feasible, safe, and cost-effective. Pediatr Blood Cancer 2010;55:1296-9. [Crossref] [PubMed]
2. Paci A, Veal G, Bardin C, et al. Review of therapeutic drug monitoring of anticancer drugs part 1--cytotoxics. Eur J Cancer 2014;50:2010-9. [Crossref] [PubMed]
3. Hamed KM, Dighriri IM, Baomar AF, et al. Overview of Methotrexate Toxicity: A Comprehensive Literature Review. Cureus 2022;14:e29518. [Crossref] [PubMed]
4. Qian Q, Hu N, Chen R, et al. Influencing Factors of Delayed Excretion After High-Dose Methotrexate in Treatment of Hematological Malignant Tumor and its Correlation with Adverse Drug Reactions. Evaluation and Analysis of Drug-Use in Hospitals of China 2020;20:56-9.
5. Boerrigter E, Crul M. A non-interventional retrospective cohort study of the interaction between methotrexate and proton pump inhibitors or aspirin. Ann Pharm Fr 2017;75:344-8. [Crossref] [PubMed]
6. Tong T, Ni WJ, Wu YQ, et al. The correlation between delayed elimination of high dose methotrexate after treatment of malignant tumor when co-administered with proton pump inhibitors. Chinese Journal of Hospital Pharmacy 2018;38:1407-10.
7. Kawase A, Yamamoto T, Egashira S, et al. Stereoselective Inhibition of Methotrexate Excretion by Glucuronides of Nonsteroidal Anti-inflammatory Drugs via Multidrug Resistance Proteins 2 and 4. J Pharmacol Exp Ther 2016;356:366-74. [Crossref] [PubMed]
8. Zhang Y, Sun L, Chen X, et al. A Systematic Review of Population Pharmacokinetic Models of Methotrexate. Eur J Drug Metab Pharmacokinet 2022;47:143-64. [Crossref] [PubMed]
9. Song Z, Hu Y, Liu S, et al. Medication therapy of high-dose methotrexate: An evidence-based practice guideline of the Division of Therapeutic Drug Monitoring, Chinese Pharmacological Society. Br J Clin Pharmacol 2022;88:2456-72. [Crossref] [PubMed]
10. Wang K, Liu CC, Mao AY, et al. Analysis on the demand, access and related factors of cancer prevention and treatment knowledge among urban residents in China from 2015 to 2017. Zhonghua Yu Fang Yi Xue Za Zhi 2020;54:84-91. [Crossref] [PubMed]
11. Dong WC, Guo JL, Wu XK, et al. Relationship Between the Free and Total Methotrexate Plasma Concentration in Children and Application to Predict the Toxicity of HD-MTX. Front Pharmacol 2021;12:636975. [Crossref] [PubMed]
12. US Department of Health and Human Services. Common Terminology Criteria for Adverse Events v4.0 (CTCAE). Cancer Therapy Evaluation Program, Common Terminology for Adverse Events, version30.5-28-2009. Bethesda, MD: National Cancer Institute, 2009. Accessed on: July 20, 2017. Available online: https://ctep.cancer.gov/protocol/Development/electronic_applications/ctc
13. Liao C, Nie J, Xu XJ, et al. The effect of the plasma methotrexate concentration during high-dose methotrexate therapy in childhood acute lymphoblastic leukemia. Leuk Lymphoma 2024;65:91-9. [Crossref] [PubMed]
14. Xu J, Li TY, Xu KK. Analysis of delayed excretion in children with acute lymphoblastic leukemia treated with high dose methotrexate. Anhui Medical and Pharmaceutical Journal 2009;13:1554-5.
15. Li X, Guo Q, Wang LZ, et al. Influencing factors of delayed methotrexate excretion in children with acute lymphoblastic leukemia. Chinese Journal of Hospital Pharmacy 2022;42:2144-7.
16. Xu WQ, Tang YM, Fang QM, et al. Delayed excretion of children with acute lymphoblastic leukemia treated with high dose methotrexate. The Chinese Journal of Hematology 2005;26:15-8.
17. Nakano T, Kobayashi R, Matsushima S, et al. Risk factors for delayed elimination of high-dose methotrexate in childhood acute lymphoblastic leukemia and lymphoma. Int J Hematol 2021;113:744-50. [Crossref] [PubMed]
18. Li SC, Wang Y, Chen YJ, et al. Analysis of correlation factors on AUC at terminal elimination phase of high dose methotrexate. Chinese Journal of Hospital Pharmacy 2016;36:1988-92.
19. Odoul F, Le Guellec C, Lamagnère JP, et al. Prediction of methotrexate elimination after high dose infusion in children with acute lymphoblastic leukaemia using a population pharmacokinetic approach. Fundam Clin Pharmacol 1999;13:595-604. [Crossref] [PubMed]
20. Foster JH, Thompson PA, Bernhardt MB, et al. A prospective study of a simple algorithm to individually dose high-dose methotrexate for children with leukemia at risk for methotrexate toxicities. Cancer Chemother Pharmacol 2019;83:349-60. [Crossref] [PubMed]
21. Tsurusawa M, Gosho M, Mori T, et al. Statistical analysis of relation between plasma methotrexate concentration and toxicity in high-dose methotrexate therapy of childhood nonHodgkin lymphoma. Pediatr Blood Cancer 2015;62:279-84. [Crossref] [PubMed]
22. Jiang ZP, Peng Q, He LM, et al. Clinical Analysis of Adverse Drug Reasctions of High-dose Methotrexate in Children with Acute Lymphoblastic Leukemia. Chinese Journal of Pharmacovigilance 2019;16:13-7.