Comparable efficacy with varying dosages of glucarpidase in pediatric oncology patients

Use of glucarpidase (carboxypeptidase-G2) in pediatric cancer patients: 11-year experience of a tertiary center

Methotrexate is an essential drug in the treatment of childhood cancer that is not exempt from toxicities. Glucarpidase is a drug used to reduce the toxic concentration of plasma methotrexate in patients with delayed elimination or at risk of toxicity. We describe the characteristics of a cohort of pediatric patients that received glucarpidase and analyze its role in the treatment of toxicity induced by high doses of methotrexate (HDMTX). Retrospective observational study of all pediatric cancer patients who received glucarpidase between 2012 and 2022 at a single center. Fifteen patients were treated with a single dose of glucarpidase, eleven of them presented with acute lymphoblastic leukemia and received HDMTX at 5 g/m2 in 24-hour infusion. In eight patients, glucarpidase was administered during the first cycle of HDMTX. The indication in thirteen cases was acute renal failure with delayed elimination of plasma methotrexate. The median maximum creatinine was 1.22 mg/dl (0.68 2.01 mg/dl), with a median increase over its baseline level of 313%. All patients normalized renal function after glucarpidase administration, with a median methotrexate excretion time of 193 hours (42-312 hours). No grade ≥2 adverse events derived from carboxypeptidase administration. Eleven patients received new doses of HDMTX in subsequent cycles, without new episodes of serious toxicity. The use of glucarpidase is effective and safe in the treatment of acute renal failure and methotrexate elimination delay in pediatric cancer patients. Further HDMTX doses may be prescribed without additional toxicities.

Case Report: Serum methotrexate monitoring by immunoassay: confusion by by-product, confusion by antidote

Methotrexate is a commonly used agent in the treatment of many malignancies and rheumatologic/inflammatory diseases. Working by inhibiting dihydrofolate reductase and thereby preventing eventual formation of tetrahydrofolate, methotrexate inhibits synthesis of purines and thymidylate, therefore disabling a malignant cell's ability to replicate. While it is able to effectively do this, methotrexate also holds potential for significant toxicity. Therefore, serum methotrexate monitoring is of utmost importance when administering the drug, particularly when high doses are used. Although there are several different measurement systems, the immunoassay is a commonly used monitoring system that may be prone to interference when using agents with similar carbon backbone as methotrexate, including folinic acid (leucovorin) at high doses, as well as in the setting of glucarpidase use and consequent methotrexate breakdown. However, adjusting leucovorin dosing policy and being aware of the potential of the immunoassay to be "confused" by similar molecules have allowed for the efficient and effective use of the immunoassay while preventing prolonged hospital stays at our institution.

The use of glucarpidase as a rescue therapy for high dose methotrexate toxicity - a review of pharmacological and clinical data

INTRODUCTION

This review aims to summarize recent data on the pharmacodynamic, pharmacokinetic, and safety of glucarpidase. This is an enzymatic agent that catalyzes the conversion of methotrexate (MTX) into inactive metabolites. Glucarpidase is used to manage high-dose MTX (HDMTX) toxic plasma concentration, especially in patients with impaired renal function.

AREAS COVERED

In this review, studies on glucarpidase clinical efficacy as a therapeutic option for patients suffering from MTX kidney toxicity were presented. Pharmacodynamic and pharmacokinetic properties of glucarpidase were included. Moreover, potential interactions and safety issues were discussed.

EXPERT OPINION

The use of glucarpidase is an effective therapeutic strategy in both adults and children treated with high doses of MTX for various types of cancer who have developed acute renal failure. Glucarpidase causes MTX to be converted to nontoxic metabolites and accelerates the time for its complete elimination. After administration of glucarpidase, it is possible to resume HDMTX.

A pooled subgroup analysis of glucarpidase treatment in 86 pediatric, adolescent, and young adult patients receiving high-dose methotrexate therapy in open-label trials

BACKGROUND

Delayed methotrexate elimination can occur in patients undergoing high-dose methotrexate cancer treatment. Effectiveness of glucarpidase for rapidly reducing methotrexate concentrations was shown in compassionate-use trials in patients aged 0-84 years.

METHODS

We performed post hoc analyses of infants (≥28 days to <2 years), children (≥2 to <12 years), adolescents (≥12 to <15 years), and young adults (≥15 to <25 years) from four multicenter, open-label, single-arm, glucarpidase compassionate-use trials. Patients had toxic methotrexate levels due to delayed methotrexate elimination and/or renal dysfunction, and received glucarpidase (50 U/kg). The primary endpoint was clinically important reduction (CIR) in plasma methotrexate (methotrexate ≤1 μmol/L at all post-glucarpidase measurements) based on high-performance liquid chromatography.

RESULTS

Among 86 patients included in efficacy analyses, CIR was achieved by zero of one infant (0.0%), five of 16 children (31.3%), seven of 24 adolescents (29.2%), and 26/45 young adults (57.8%). Median methotrexate reduction was 98.7% or higher in each group 15 minutes post-glucarpidase. Patients with pre-glucarpidase methotrexate less than 50 μmol/L (35/42, 83.3%) were more likely to achieve CIR than those with methotrexate 50 μmol/L or higher (1/37, 2.7%). The most common treatment-related adverse event was paresthesia, occurring in three adolescents (4.5%) and six young adults (5.2%). No other treatment-related adverse event occurred in 5% or higher of any age group.

CONCLUSION

After accounting for pre-glucarpidase methotrexate levels, glucarpidase efficacy at inducing CIR in pediatric/young adult patients was consistent, with efficacy observed in the overall study population (i.e., patients aged 0-84), and no unexpected safety findings were observed. These findings demonstrate glucarpidase (50 U/kg) is an effective and well-tolerated dose for pediatric, adolescent, and young adult patients.

Extracorporeal Treatment for Methotrexate Poisoning: Systematic Review and Recommendations from the EXTRIP Workgroup

Methotrexate is used in the treatment of many malignancies, rheumatological diseases, and inflammatory bowel disease. Toxicity from use is associated with severe morbidity and mortality. Rescue treatments include intravenous hydration, folinic acid, and, in some centers, glucarpidase. We conducted systematic reviews of the literature following published EXtracorporeal TReatments In Poisoning (EXTRIP) methods to determine the utility of extracorporeal treatments in the management of methotrexate toxicity. The quality of the evidence and the strength of recommendations (either "strong" or "weak/conditional") were graded according to the GRADE approach. A formal voting process using a modified Delphi method assessed the level of agreement between panelists on the final recommendations. A total of 92 articles met inclusion criteria. Toxicokinetic data were available on 90 patients (89 with impaired kidney function). Methotrexate was considered to be moderately dialyzable by intermittent hemodialysis. Data were available for clinical analysis on 109 patients (high-dose methotrexate [>0.5 g/m²]: 91 patients; low-dose [≤0.5 g/m²]: 18). Overall mortality in these publications was 19.5% and 26.7% in those with high-dose and low-dose methotrexate-related toxicity, respectively. Although one observational study reported lower mortality in patients treated with glucarpidase compared with those treated with hemodialysis, there were important limitations in the study. For patients with severe methotrexate toxicity receiving standard care, the EXTRIP workgroup: (1) suggested against extracorporeal treatments when glucarpidase is not administered; (2) recommended against extracorporeal treatments when glucarpidase is administered; and (3) recommended against extracorporeal treatments instead of administering glucarpidase. The quality of evidence for these recommendations was very low. Rationales for these recommendations included: (1) extracorporeal treatments mainly remove drugs in the intravascular compartment, whereas methotrexate rapidly distributes into cells; (2) extracorporeal treatments remove folinic acid; (3) in rare cases where fast removal of methotrexate is required, glucarpidase will outperform any extracorporeal treatment; and (4) extracorporeal treatments do not appear to reduce the incidence and magnitude of methotrexate toxicity.

Routine use of low-dose glucarpidase following high-dose methotrexate in adult patients with CNS lymphoma: an open-label, multi-center phase I study

Background

High-dose methotrexate (HD-MTX) has broad use in the treatment of central nervous system (CNS) malignancies but confers significant toxicity without inpatient hydration and monitoring. Glucarpidase is a bacterial recombinant enzyme dosed at 50 units (u)/kg, resulting in rapid systemic MTX clearance. The aim of this study was to demonstrate feasibility of low-dose glucarpidase to facilitate MTX clearance in patients with CNS lymphoma (CNSL).

Methods

Eight CNSL patients received HD-MTX 3 or 6 g/m² and glucarpidase 2000 or 1000u 24 h later. Treatments repeated every 2 weeks up to 8 cycles.

Results

Fifty-five treatments were administered. Glucarpidase 2000u yielded > 95% reduction in plasma MTX within 15 min following 33/34 doses (97.1%) and glucarpidase 1000u yielded > 95% reduction following 15/20 doses (75%). Anti-glucarpidase antibodies developed in 4 patients and were associated with MTX rebound. In CSF, glucarpidase was not detected and MTX levels remained cytotoxic after 1 (3299.5 nmol/L, n = 8) and 6 h (1254.7 nmol/L, n = 7). Treatment was safe and well-tolerated. Radiographic responses in 6 of 8 patients (75%) were as expected following MTX-based therapy.

Conclusions

This study demonstrates feasibility of planned-use low-dose glucarpidase for MTX clearance and supports the hypothesis that glucarpidase does not impact MTX efficacy in the CNS.

Clinical trial registration

NCT03684980 (Registration date 26/09/2018).

Effective elimination of high-dose methotrexate by repeated hemodiafiltration and high-flux hemodialysis in patients with acute kidney injury

INTRODUCTION

Acute kidney injury (AKI) after high dose methotrexate (HD-MTX) is associated with delayed MTX-excretion and life-threatening toxicity. Glucapridase, the recommended therapy, is expensive and not always available.

CASE SERIES

We describe 3 cases (69, 67, 73 years) with diffuse large B-cell lymphoma who developed AKI and early-onset severely delayed MTX elimination after HD-MTX. MTX serum concentrations were 101 and 69 μmol/L at 24 h after administration in two patients and 34 μmol/L at 32 h in the third.

MANAGEMENT AND OUTCOME

Since glucarpidase was unavailable, we performed daily high-flux hemodialysis (HF-HD) or online hemodiafiltration (HDF) sessions (median duration, 6 h). The median serum MTX elimination half-life during HDF/HF-HD sessions was similar in all patients (median, 4.4 h; IQR, 3.8-5.3 h), but serum MTX concentrations rebounded after each dialysis by a median of 40% of the trough concentrations. The three patients underwent multiple dialysis sessions, until MTX serum concentrations remained sufficiently low to be neutralized by leucovorin. Only 1 patient developed severe pancytopenia, and renal function normalized in all patients after 3-6 weeks.

DISCUSSION

In conclusion, when glucarpidase is unavailable or delayed, early, repeated and prolonged HDF/HF-HD effectively enhance MTX elimination and prevent toxicity in patients with AKI and severely delayed MTX elimination after HD-MTX.

Half-dose glucarpidase as efficient rescue for toxic methotrexate levels in patients with acute kidney injury

Purpose

High-dose methotrexate (HDMTX)-associated acute kidney injury with delayed MTX clearance has been linked to an excess in MTX-induced toxicities. Glucarpidase is a recombinant enzyme that rapidly hydrolyzes MTX into non-toxic metabolites. The recommended dose of glucarpidase is 50 U/kg, which has never been formally established in a dose finding study in humans. Few case reports, mostly in children, suggest that lower doses of glucarpidase might be equally effective in lowering MTX levels.

Methods

Seven patients with toxic MTX plasma concentrations following HDMTX therapy were treated with half-dose glucarpidase (mean 25 U/kg, range 17–32 U/kg). MTX levels were measured immunologically as well as by liquid chromatography–mass spectrometry (LC–MS). Toxicities were assessed according to National Cancer Institute—Common Terminology Criteria for Adverse Events (CTCAE) v5.0.

Results

All patients experienced HDMTX-associated kidney injury (median increase in creatinine levels within 48 h after HDMTX initiation compared to baseline of 251%, range 80–455%) and showed toxic MTX plasma concentrations (range 3.1–182.4 µmol/L) before glucarpidase injection. The drug was administered 42–70 h after HDMTX initiation. Within one day after glucarpidase injection, MTX plasma concentrations decreased by ≥ 97.7% translating into levels of 0.02–2.03 µmol/L. MTX rebound was detected in plasma 42–73 h after glucarpidase initiation, but concentrations remained consistent at < 10 µmol/L.

Conclusion

Half-dose glucarpidase seems to be effective in lowering MTX levels to concentrations manageable with continued intensified folinic acid rescue.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00280-021-04361-8.

A second administration of glucarpidase in a different cycle of high-dose methotrexate: Is it safe and effective in adults?

INTRODUCTION

Methotrexate intoxication following high-dose methotrexate-induced acute kidney injury is a life-threatening complication. Glucarpidase can quickly reduce extracellular methotrexate to safe levels, but the effectiveness and safety of its use in different episodes of nephrotoxicity remain an unknown area.

CASE REPORT

A 30-year-old male diagnosed with acute lymphoblastic T-cell lymphoma received methotrexate 5 g/m2 intravenous (IV) as part of the first consolidation cycle. On Consolidation 3, he restarted methotrexate at a dose of 3 g/m2 IV showing slow methotrexate elimination, associated myelosuppression, and hepatic toxicity. Glucarpidase was administered (total dose of 2000 International Units (IU)). No adverse events were observed, and his renal function returned to normal. One hundred and six days later, he was diagnosed with leptomeningeal and cerebellar relapse and treatment with methotrexate 3,5 g/m2 IV day 1 and cytosine arabinoside (Ara-C) 2 g/m2 IV twice per day days 1, 3, and 5 was started. At 36 h from methotrexate infusion, serum creatinine increased up to 1.89 mg/dL and methotrexate concentration was 100 µmol/L.Management and Outcome: Ara-C was suspended, and a second administration of glucarpidase (2000 IU) was dispensed. No adverse events were noticed, methotrexate levels decreased and renal function progressively improved, recovering completely three weeks later.

DISCUSSION

The effectiveness and safety of the use of glucarpidase in different episodes of nephrotoxicity remain an unknown area, and the rate and consequences of antiglucarpidase antibody formation remain poorly understood. This case report is, to our knowledge, the first case of a second administration of glucarpidase in a different cycle of high-dose methotrexate in an adult patient.

Successful Treatment of Delayed Methotrexate Clearance Using Glucarpidase Dosed on Ideal Body Weight in Obese Patients

Delayed methotrexate (MTX) elimination after treatment with high-dose (HD) MTX may result in life-threatening toxicities as well as acute kidney injury (AKI). Treatment includes administration of glucarpidase, an enzyme that rapidly inactivates MTX. Dosing of glucarpidase is based on body weight; however, recommendations for dosage adjustments in obese patients are lacking. We describe three obese adult patients (body mass index [BMI] range 31-43 kg/m² ) who received HD-MTX following all precautions for its treatment. Although peak MTX concentrations were within the expected range (308-368 µmol/L), MTX concentrations after 24 hours or later were markedly increased (97, 52, and 19 µmol/L, respectively). Two patients experienced AKI. After a single intravenous dose of glucarpidase 4000 units (50 units/kg on the basis of ideal body weight [IBW]) was administered to each patient 38, 46, and 60 hours, respectively, after the start of MTX, MTX concentrations dropped quickly to 1.37, 0.07, and 0.03 µmol/L, respectively, and further decreased steadily. Over time, clinical status and renal function improved in all patients. Glucarpidase is a highly hydrophilic molecule with a volume of distribution of 3.6 L, representing the intravascular volume of an adult. Therefore, we used IBW for glucarpidase dose calculations, allowing us to reduce the dose that would have been determined by using total body weight. This approach resulted in a rapid decrease of MTX serum concentrations and may reduce treatment costs of this highly expensive drug.

DAMPAned Methotrexate: A Case Report and Review of the Management of Acute Methotrexate Toxicity

Rationale

Consensus guidelines on the management of methotrexate-induced nephrotoxicity using glucarpidase (Voraxaze) may be relatively unfamiliar to the nephrology community.

Presenting concerns of the patient

A 61-year-old man with intravascular large B-cell lymphoma was admitted for cycle #1 of high-dose methotrexate (HDMTX) following 2 cycles of R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone) chemotherapy. On admission, he was clinically euvolemic and had a creatinine clearance of 98 mL/min. He received standard HDMTX toxicity prophylaxis with volume expansion, urinary alkalinization, and leucovorin rescue.

Diagnoses

Despite prophylactic efforts, he developed a severe acute kidney injury, creatinine 63 to 226 µmol/L (2.56 mg/dL), following HDMTX, impaired methotrexate clearance, and neurotoxicity manifested by status epilepticus.

Interventions

He was given glucarpidase to convert extracellular methotrexate into its inactive metabolites, glutamate and DAMPA (4-deoxy-4-amino-N ¹⁰-methylpteroic acid) at 52 hours post-HDMTX. Cross-reactivity between commercial methotrexate immunoassays with DAMPA led to falsely elevated methotrexate concentrations for much longer than expected based on the current guideline (5 days instead of <48 hours). This required ongoing monitoring of methotrexate concentration by mass spectrometry.

Outcomes

The patient remained nonoliguric and did not develop acute indications for dialysis. Serum creatinine peaked at 608 µmol/L (6.88 mg/dL) 6 days after HDMTX. He ultimately had a full renal and neurologic recovery.

Lessons learned

Glucarpidase is an effective option for nonrenal elimination of methotrexate-induced nephrotoxicity. Timing of methotrexate concentration monitoring to assess for toxicity, how to access the drug, and the need for ongoing monitoring by mass spectrometry beyond the guideline recommendation are highlighted for centers where HDMTX therapy may be used.

Cancer drug development: The missing links

IMPACT STATEMENT

The success rate for cancer drugs which enter into phase 1 clinical trials is utterly less. Why the vast majority of drugs fail is not understood but suggests that pre-clinical studies are not adequate for human diseases. In 1975, as per the Tufts Center for the Study of Drug Development, pharmaceutical industries expended 100 million dollars for research and development of the average FDA approved drug. By 2005, this figure had more than quadrupled, to $1.3 billion. In order to recover their high and risky investment cost, pharmaceutical companies charge more for their products. However, there exists no correlation between drug development cost and actual sale of the drug. This high drug development cost could be due to the reason that all patients might not respond to the drug. Hence, a given drug has to be tested in large number of patients to show drug benefits and obtain significant results.

Management of Patients with Acute Methotrexate Nephrotoxicity with High-Dose Leucovorin

BACKGROUND

Acute kidney injury complicating high-dose methotrexate (HDMTX) therapy increases the risk for severe mucositis, myelosuppression, and death. It is unclear whether high-dose leucovorin and supportive therapy without the use of glucarpidase can reduce toxicity from HDMTX.

STUDY DESIGN

The charts of all patients at Memorial Sloan Kettering Cancer Center whose methotrexate (MTX) drug levels at 48 or 72 hours after administration were 10 times or more the toxic level were reviewed between January 2000 and December 2011.

RESULTS

Eighty-eight patients (median age 51 years, range 9-90 years) who received 100 courses of HDMTX were identified. Serum creatinine increased by 2-fold from baseline (median, range 1- to 10-fold), but all patients recovered kidney function. Serum levels of MTX were 69 μmol/L (median, range 2.2-400), 6.9 μmol/L (1.3-64), and 2.0 μmol/L (0.05-26) at 24, 48, and 72 hours, respectively, after administration. A statistically significant correlation existed between MTX levels at 48, 72, 96, and 120 hours after administration but not between 24 and 72 hours or subsequent time points. High-dose leucovorin was given in 81% of courses in accordance with institutional protocols in most cases. Myelosuppression was present in 42%; grade III or higher neutropenia in 29%, and thrombocytopenia in 25%. Infectious complications, oral mucositis, and diarrhea occurred in 21%, 17%, and 6% of patients, respectively. Five deaths occurred, none directly attributed to complications from MTX administration. Seven additional patients received glucarpidase at the discretion of a treating physician during the study period, and results are reported separately.

CONCLUSION

Patients who had 100 episodes of HDMTX-associated acute kidney injury were treated with a strategy that only included usual supportive measures and high-dose leucovorin. No deaths were directly attributed to complications related to HDMTX. Glucarpidase, an expensive drug, may not be necessary for a significant number of patients.

Delayed Methotrexate Clearance Despite Carboxypeptidase-G2 (Glucarpidase) Administration in 2 Patients With Toxic Methotrexate Levels

High-dose methotrexate has been a treatment for osteosarcoma; however, its nephrotoxic effects are considerable. Carboxypeptidase-G2 (glucarpidase) was approved by the US Food and Drug Administration in 2012 for treatment of toxic methotrexate levels. We report our experience using glucarpidase under compassionate use before Food and Drug Administration approval in 2 patients who had delayed methotrexate clearance and prolonged kidney injury despite glucarpidase administration. Our results show that patients with methotrexate toxicity may require repeated doses of glucarpidase in addition to supportive measures, such as dialysis.

Consensus Guideline for Use of Glucarpidase in Patients with High-Dose Methotrexate Induced Acute Kidney Injury and Delayed Methotrexate Clearance

An expert panel was convened to provide specific, expert consensus guidelines for the use of glucarpidase in patients who develop high‐dose methotrexate (HDMTX)‐induced nephrotoxicity and delayed methotrexate excretion. This guideline provides recommendations to identify the population of patients who would benefit from glucarpidase rescue by more precisely defining the absolute methotrexate concentrations associated with risk for severe or life‐threatening toxicity at several time points after the start of a HDMTX infusion.

Acute kidney injury due to high‐dose methotrexate (HDMTX) is a serious, life‐threatening toxicity that can occur in pediatric and adult patients. Glucarpidase is a treatment approved by the Food and Drug Administration for high methotrexate concentrations in the context of kidney dysfunction, but the guidelines for when to use it are unclear. An expert panel was convened to provide specific, expert consensus guidelines for the use of glucarpidase in patients who develop HDMTX‐induced nephrotoxicity and delayed methotrexate excretion. The guideline provides recommendations to identify the population of patients who would benefit from glucarpidase rescue by more precisely defining the absolute methotrexate concentrations associated with risk for severe or life‐threatening toxicity at several time points after the start of an HDMTX infusion. For an HDMTX infusion ≤24 hours, if the 36‐hour concentration is above 30 µM, 42‐hour concentration is above 10 µM, or 48‐hour concentration is above 5 µM and the serum creatinine is significantly elevated relative to the baseline measurement (indicative of HDMTX‐induced acute kidney injury), glucarpidase may be indicated. After a 36‐ to 42‐hour HDMTX infusion, glucarpidase may be indicated when the 48‐hour methotrexate concentration is above 5 µM. Administration of glucarpidase should optimally occur within 48–60 hours from the start of the HDMTX infusion, because life‐threatening toxicities may not be preventable beyond this time point.

Implications for Practice.

Glucarpidase is a rarely used medication that is less effective when given after more than 60 hours of exposure to high‐dose methotrexate, so predicting early which patients will need it is imperative. There are no currently available consensus guidelines for the use of this medication. The indication on the label does not give specific methotrexate concentrations above which it should be used. An international group of experts was convened to develop a consensus guideline that was specific and evidence‐based to identify the population of patients who would benefit from glucarpidase.

Delayed elimination of high-dose methotrexate and use of carboxypeptidase G2 in pediatric patients during treatment for acute lymphoblastic leukemia

BACKGROUND

Carboxypeptidase G2 (CPDG₂ ) can be used as rescue treatment in cases of delayed methotrexate elimination (DME) and Mtx-induced nephrotoxicity.

PROCEDURE

Between July 2008 and December 2014, all children (1.0-17.9 years) in the Nordic countries diagnosed with Philadelphia chromosome negative acute lymphoblastic leukemia (ALL) were treated according to the Nordic Organization for Pediatric Hematology and Oncology (NOPHO) ALL 2008 protocol, including administration of six to eight high-dose (5 g/m² /24 hr) Mtx (HDMtx) courses. The protocol includes recommendations for CPDG₂ administration in cases of DME (clinicaltrials.gov NCT01305655).

RESULTS

Forty-seven of the 1,286 children (3.6%) received CPDG₂ during 50 HDMtx courses at a median dose of 50 IU/kg. In 49% of the cases, CPDG₂ was used during the first HDMtx course. Within a median of 6 hr from CPDG₂ administration, the Mtx concentration decreased by 75% when measured with immune-based methods, and by 100% when measured with high-performance liquid chromatography. The median time from the start of Mtx infusion to plasma levels ≤ 0.2 μM was 228 hr (range: 48-438). The maximum increase in plasma creatinine was 375% (range: 100-1,310). Creatinine peaked after a median of 48 hr (range: 36-86). Mtx elimination time was shorter in patients with body surface area < 1 m² (median 198.5 vs. 257 hr; P = 0.004) and was inversely correlated to the maximum creatinine increase (209 vs. 258 hr; P = 0.034). All patients normalized their renal function as measured with s-creatinine.

CONCLUSIONS

CPDG₂ administration is highly effective as rescue in case of delayed Mtx clearance. Subsequent HDMtx courses could be administered without events in most of the patients.