Abstract
Early identification of methotrexate-induced acute kidney injury (AKI) and delayed elimination of methotrexate are critical to limiting toxicity of the drug. The current monitoring strategy consists of serial serum methotrexate concentrations at 24, 36, 42, and 48 hours. Appropriate serum concentration monitoring and intervention does not always prevent AKI. Therefore, ongoing study of biomarkers and improved methods of screening for methotrexate-induced AKI is critical to reduce toxicity. This case series reports urine methotrexate values of 4 patients undergoing treatment with high-dose methotrexate. Urine methotrexate concentration was measured 46 to 48 hours after methotrexate infusion. Urine methotrexate concentration was compared with the duration of drug clearance from the serum. Only 1 patient (case 3) developed AKI. Serum concentration of methotrexate were < 0.3 μmol/L at 42, 48, and 48 hours in patients 1, 2, and 4, respectively, and at 168 hours in patient 3 (p < 0.01). Urine methotrexate concentrations were 2.77, 6.45, and 7.8 (μmol/L), in patients 1, 2, and 4, respectively, and 113.69 (μmol/L) in patient 3 (p < 0.001). This case series provides preliminary data that urine methotrexate concentration at hours 46 to 48 may reflect AKI. Future studies should investigate the ability of serial urine methotrexate concentrations to predict delayed drug clearance and the development of AKI.
Keywords: acute kidney injury, acute lymphoblastic lymphoma, adverse drug reaction, high-dose methotrexate, side effect, toxicology
Introduction
High-dose methotrexate with timed citrovorum factor rescue is a major component of acute lymphocytic leukemia, T-cell lymphoblastic lymphoma, and osteosarcoma treatment.1,2 Toxic effects of methotrexate include anemia, neutropenia, thrombocytopenia, oral mucositis, enteritis, and hepatic injury.3–6 Methotrexate may also cause crystals to form within the kidney resulting in acute renal injury (AKI). Acute kidney injury (serum creatinine > 125% of baseline) may occur during or shortly after drug infusion.7 As kidney injury progresses, uric acid crystal formation may also occur. Metabolic toxicities and impaired repair mechanisms may further compromise renal function. This cascade of events may result in irreversible kidney damage and subsequent chronic renal failure.
The risk of methotrexate associated metabolic toxici-ties can be reduced by hydration, urinary alkalization, and timed citrovorum factor (e.g., folinic acid) rescue.6 Although the risk of AKI can be significantly reduced by these same interventions, AKI is a more complex problem that is often difficult to predict and treat. Known risk factors for methotrexate-induced AKI include antecedent enteritis, and renal injury during prior courses of therapy.8 Additional risk markers include a rise in serum creatinine and a plateau in the methotrexate elimination curve with or without a decrease in urine output.7 Once established, methotrexate-induced AKI cannot be reversed without dissolution of methotrexate crystals in the kidney by carboxypeptidase.9 Carboxypeptidase is often not immediately available in most pharmacies due to its high cost. This may delay the initiation of treatment, thereby increasing risk.
Current practice includes monitoring serum creati-nine and methotrexate elimination via serum concentration monitoring. These values are used to inform interventions including hydration, carboxypeptidase, and extension of leucovorin duration. Interventions such as hydration are based on the concentrations of serum methotrexate and creatinine, which are drawn at 24, 36, 42, and 48 hours at our institution. Despite careful monitoring in the hospital setting, significant nephrotoxicity, delayed elimination of methotrexate, and associated mucositis, hepatotoxicity, and enteritis represent major risks. An ideal monitoring system would allow for immediate and accurate prediction and intervention to prevent methotrexate-induced AKI. Although the role of biomarkers (e.g., cystatin C) are actively being investigated, urine methotrexate concentration has received little attention in the literature.
Early identification of methotrexate-induced AKI is critical to ensuring that carboxypeptidase is available for prompt administration. In this case series, we report evidence that there is a relationship between serum and urine methotrexate concentrations. This case report suggests a relationship between methotrexate-induced acute renal injury, serum creatinine, and urinary methotrexate concentrations.
Methods
Patients were included if they 1) were diagnosed with high-risk B-cell acute lymphoblastic leukemia (B-ALL); 2) had been treated according to the Children's Oncology Group (COG) AALL 0631 (NCT00557193) and/or COG AALL 1131 protocols (NCT02883049); and 3) received high-dose methotrexate defined as 500 mg/m2 IV over 30 minutes and 4500 mg/m2 by continuous infusion over the next 23.5 hours. Patients were excluded if they 1) had known antecedent renal disease; 2) had received nephrotoxic agents (e.g., non-steroidal anti-inflammatory drugs and trimethoprim/sulfamethoxazole) 24 hours before methotrexate initiation and for the duration of their admission; and/or 3) they had an elevated serum creatinine at the time methotrexate was begun (>125% of patient baseline).10,11
Serum methotrexate concentrations were serially determined from the beginning of drug infusion until drug clearance (<0.3 μmol/L) was achieved. Time to clearance was recorded. Regardless of clearance rates, double-voided urine methotrexate concentrations were collected at 48 hours post-infusion (range, 46–48 hours) and were used to determine urine methotrexate concentrations. Time to clearance and time of sample collection were measured from the start of methotrexate infusion (i.e., hour 48 was 24 hours after completion of the 24-hour infusion).
Because this was a preliminary study, the authors felt it was important to explore the relationship between urine methotrexate concentrations and development of AKI. The 48-hour time point was selected to investigate whether or not concentration of methotrexate in the urine was reflective of AKI.
Double-voided samples were used to ensure that the measured concentration reflected the urine methotrexate concentration at the time of collection. In short, adult patients were asked to completely void; several minutes later, we had these patients provide a second sample that was used for testing. Pediatric patients received a catheterization; several minutes later, a second catheterization was used to collect the specimen for testing. Urine methotrexate concentrations were measured using the ARK methotrexate assay (ARK Diagnostics, Inc, Fremont, CA). This ARK assay is investigational for urine samples. This methodology was validated by our instrumentation and is being used at other facilities.
Serum methotrexate and serum creatinine concentrations were collected according to COG study and protocol guidelines at 24, 42, and 48 hours after initiation of the infusion. Patients with a serum methotrexate concentration ≥ 150 μmol/L or a creatinine > 125% of baseline had laboratory tests repeated at 36 hours. Serum methotrexate concentrations and urine methotrexate concentrations were both evaluated with the ABBOTT ci8200 analyzer (Abbott Park, IL). ARK reagent, calibrators, and quality control materials were used in an open channel format according to manufacturer specifications. Controls were run every 8 hours of specimen testing.
Acute kidney injury was defined by a rise of serum creatinine >125% of baseline. A statistician was consulted to determine whether duration of clearance or urine methotrexate concentrations among any patient was an outlier. The validity of difference between data points was assessed independently assuming both normal and non-normal distribution. Grubbs test and Rosner procedure were used assuming normal distribution. The IQR was used to assess the data assuming non-normal distribution. Following the rules of IQR, if any data point was >1.5 IQRs from the 75th percentile, it was considered an outlier.
Results
Four patients met our study criteria. Subject characteristics are summarized in the Table. High-dose methotrexate was administered over a 24-hour period, with a 500-mg/m2 bolus given over the first 30 minutes and a 4500-mg/m2 continuous infusion administered over the remaining 23.5 hours. All patients were given supportive therapy according to COG guidelines (i.e., hydration, urinary alkalization) and maintained a urine pH > 7 during the duration of their therapy.
Table.
Patient Information and Laboratory Data
| Patient | Patient Demographics | Diagnosis and Disease Features | Chemotherapy Protocol and Phase | Serum Methotrexate Concentration*, μmol/L | Time Until Serum Methotrexate < 0.3 μmol/L*, hr | Time of Urine Collection*, hr | Double-Voided Urine Methotrexate Concentration, μmol/L |
|---|---|---|---|---|---|---|---|
| 1 | 10-mo-old female | High-risk B acute; pre-B ALL | COG AALL 0631 Consolidation: cycle 4 | 24 hr: 118 42 hr: 0.46 48 hr: 0.20 | 48 | 48 | 2.77 |
| 2 | 22-yr-old female | High-risk B-ALL; IKZF1 and CDKN2A positive | COG AALL 1131 Interim maintenance 1 | 24 hr: 1.03 36 hr: 0.67 48 hr: 0.29 | 48 | 48 | 6.45 |
| 3† | 28-yr-old male | High-risk pre-B-ALL | COG AALL 1131 Interim maintenance 1 | 24 hr: 176 36 hr: 38.93 40 hr: 24.26 48 hr: 16.38 54 hr: 13.66 78 hr: 1.52 7 days: 0.26 7.5 days: 0.23 | 168 | 46 | 113.69 |
| 4 | 3-yr-old male | High-risk B-ALL; hyperploidy (54 XY) trisomy 10, tetrasomy 14 and 21, and a 2;14;18 translocation | COG AALL 1131 Interim maintenance 1 | 24 hr: 72.14 32 hr: 0.78 42 hr: 0.23 48 hr: 0.16 54 hr: 0.09 | 42 | 46 | 7.8 |
B-ALL, ; CDKN2A, cyclin dependent kinase inhibitor 2A; COG, ;IKZF1, IKAROS Family Zinc Finger 1
*After methotrexate initiation.
† Patient with clinically significant methotrexate renal toxicity.
The duration of clearance and double-voided urine methotrexate concentrations are listed in the Table and depicted in Figure 1. Patients 1, 2, and 4 maintained healthy renal function during treatment. Patient 3 developed methotrexate-induced AKI. His serum creatinine reached the threshold for diagnosis of AKI (>125% of baseline) at 36 hours (Figure 2). Serum creatinine values of all 4 patients are represented in Figure 2. In patients 1, 2, and 4, who did not experience AKI, methotrexate was below 0.3 μmol/L from serum in 42, 48, and 48 hours, respectively. Patient 3, who experienced AKI, did not clear methotrexate until after 168 hours. This was calculated to be an outlier under normal (p < 0.01) and non-normal (17 IQRs outside of expected values). Patients 1, 2, and 4 had urine methotrexate concentrations of 2.77, 6.45, and 7.8 μmol/L, respectively, at 46 to 48 hours (Table). Patient 3 had a urine methotrexate concentration of 113.69 μmol/L, which was also calculated to be an outlier under normal (p < 0.005) and non-normal (21 IQRs outside of expected values). The relationship between serum creatinine and urine methotrexate concentrations are depicted in Figure 3.
Figure 1.
Relationship between urine methotrexate and duration of clearance.
Figure 2.
Serum creatinine levels during hospital admission.
Figure 3.
Relationship between urine methotrexate concentration and serum creatinine at 48 hours.
Serum creatinine values from patient 3 peaked at 2.19 mg/dL up from 0.73 at baseline (3 ′ baseline). Patient 3 was managed per COG protocol guidelines with modifications of supportive care (i.e., hydration, alkalization, and leucovorin rescue). Despite carefully following the recommendations from COG for supportive care, the serum creatinine of Patient 3 continued to rise. An order was placed for glucarpidase. Administration of this medication was delayed due to the authorization process and shipping of the medication. Glucarpidase 2000 units was administered as a 1-time dose approximately 58 hours after initiation of infusion (Figure 2). Patient 3 had a length of stay of 15 days, compared with a length of stay of 2 to 5 days for the other 3 patients.
Discussion
In this study, 1 patient developed methotrexate-induced AKI. This patient experienced a 3- to 4-fold longer duration of clearance (p < 0.01), a serum creatinine 300% of baseline, and a 15-day length of stay. We found that double-voided urine methotrexate concentration at hours 46 to 48 post-infusion is 14- to 40-fold higher in this patient with a methotrexate-induced AKI (p < 0.005). One limitation to this study is that it does not provide serial urine methotrexate concentrations. It is possible that urine methotrexate values reached a high concentration during the infusion in patients 1, 2, and 4 (before the 46- to 48-hour time point) but did not result in AKI because of hydration and leucovorin.
These 4 patient case series suggest that urinary methotrexate concentration reflects AKI. Urine methotrexate measurements open the possibility to measuring the fractional excretion of methotrexate, similar to calculations for fractional excretion of sodium. Urine samples may have the benefit of reducing blood collections in infants undergoing chemotherapy (e.g., at risk of anemia) and reducing the risk of line infection. Our study evaluated double-voided methotrexate urine concentrations 46 to 48 hours' post-infusion; therefore, our data are reactive rather than predictive. Future studies are needed to determine if serial urine methotrexate concentration reflects the development of nephrotoxicity and is useful for monitoring for AKI.
Samples obtained at earlier time points may be predictive of renal injury. Future studies should investigate the relationship between serial serum and double-voided urine methotrexate concentrations following the initial methotrexate bolus infusion (0.5 hours) and 1 hour following completion of infusion (hour 25 – to ensure complete serum distribution). If the urine methotrexate concentration is predictive of toxicity after the 0.5-hour methotrexate bolus, earlier intervention may be indicated. If the urine methotrexate value is predictive of toxicity at hour 25, carboxypeptidase could be acquired and administered prior to further renal injury.
Conclusions
In summary, our results provide preliminary evidence that urinary concentration of methotrexate reflects AKI and may be a useful laboratory marker of methotrexate-induced AKI. Future research should focus on the utility of serial urine methotrexate concentrations at earlier time points in order to facilitate earlier intervention.
Acknowledgments
The authors would like to thank Alice Hawley, MLS (ASCP) for her noteworthy contributions to analyzing laboratory specimens and organizing data. Thanks to Timothy McManamon, MLS (ASCP) for his departmental oversight in the laboratory. Thanks to Marilyn Klug, PhD for her thoughtful guidance with statistical analysis. The authors would also like to thank Christopher Tiongson, MD and Carlina Grindeland, PharmD for providing institutional oversight for this project. Finally, thanks to the patients who agreed to participate in this study.
ABBREVIATIONS
- ALL
acute lymphoblastic leukemia
- COG
Children's Oncology Group
- IQR
interquartile range
- IV
intravenous
Footnotes
Disclosure. The authors declare no conflicts or financial interest in any product or service mentioned in the manuscript, including grants, equipment, medications, employment, gifts, and honoraria. The authors had full access to all patient information in this report and take responsibility for the integrity and accuracy of the report.
Ethical Approval and Informed Consent. This study was approved by the institutional review boards of both the University of North Dakota and Sanford Medical Center Fargo in Fargo, ND. All patients and/or families provided verbal and written consent to collect double-voided urine samples.
References
- 1.Cooper SL, Brown PA. Treatment of pediatric acute lymphoblastic leukemia. Pediatr Clin North Am. 2015;62(1):61–73. doi: 10.1016/j.pcl.2014.09.006. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.Taran SJ, Taran R, Malipatil NB. Pediatric osteosarcoma: an updated review. Indian J Med Paediatr Oncol. 2017;38(1):33–43. doi: 10.4103/0971-5851.203513. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 3.Jones KW, Patel SR. A family physician's guide to monitoring methotrexate. Am Fam Physician. 2000;62(7):1607–1612. [PubMed] [Google Scholar]
- 4.Chabner BA, Allegra CJ, Curt GA et al. Polyglutamation of methotrexate: is methotrexate a prodrug? J Clin Invest. 1985;76(3):907–912. doi: 10.1172/JCI112088. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 5.Allegra CJ, Chabner BA, Drake JC et al. Enhanced inhibition of thymidylate synthase by methotrexate polygluta-mates. J Biol Chem. 1985;260(17):9720–9726. [PubMed] [Google Scholar]
- 6.Howard SC, McCormick J, Pui CH et al. Preventing and managing toxicities of high-dose methotrexate. Oncologist. 2016;21(12):1471–1482. doi: 10.1634/theoncologist.2015-0164. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 7.Widemann BC, Adamson PC. Understanding and managing methotrexate nephrotoxicity. Oncologist. 2006;11(6):694–703. doi: 10.1634/theoncologist.11-6-694. [DOI] [PubMed] [Google Scholar]
- 8.Wiczer T, Dotson E, Tuten A et al. Evaluation of incidence and risk factors for high-dose methotrexate-induced nephrotoxicity. J Oncol Pharm Practice. 2016;22(3):430–436. doi: 10.1177/1078155215594417. [DOI] [PubMed] [Google Scholar]
- 9.Ramsey LB, Balis FM, O'Brien MM et al. Consensus guideline for use of glucarpidase in patients with high dose methotrexate induced acute kidney injury and delayed methotrexate clearance. Oncologist. 2018;23(1):52–61. doi: 10.1634/theoncologist.2017-0243. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 10.Burke MJ, Salzer WL, Devidas M et al. Replacing cyclophosphamide/cytarabine/mercaptopurine with cyclophosphamide/etoposide during consolidation/delayed intensification does not improve outcome for pediatric B-cell acute lymphoblastic leukemia: a report from the COG. Haematologica. 104(5):986–992. doi: 10.3324/haematol.2018.204545. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 11.Salzer WL, Jones TL, Devidas M et al. Decreased induction morbidity and mortality following modification to induction therapy in infants with acute lymphoblastic leukemia enrolled on AALL0631: a report from the Children's Oncology Group. Pediatr Blood Cancer. 62(3):414–418. doi: 10.1002/pbc.25311. [DOI] [PMC free article] [PubMed] [Google Scholar]