High cut-off dialysis as a salvage therapy option in high-dose methotrexate chemotherapy?

Phase 2 study of glucarpidase in patients with delayed methotrexate elimination after high-dose methotrexate therapy

PURPOSE

High-dose methotrexate therapy (HD-MTX) is a standard treatment for various malignant tumors, but approximately 1-10% of patients experience delayed MTX elimination (DME) that can induce organ damage. Glucarpidase can hydrolyze MTX and thereby lower the level of active MTX in the blood. A multicenter, open-label, phase II investigator-initiated trial (CPG2-PII study) was conducted to evaluate glucarpidase rescue therapy in Japanese patients who showed DME after HD-MTX treatment. To confirm the robustness of this therapy, further corporate-sponsored clinical trial (OP-07-001 study) was conducted.

METHODS

The primary endpoint in the CPG2-PII study was to evaluate the proportion of patients of the percentage clinical important reduction (CIR) as an indicator of MTX concentration, which can be managed with leucovorin and supportive care. The primary endpoint of the OP-07-001 study was to evaluate the decreasing rate of plasma MTX concentration at 20 min after glucarpidase administration from the baseline for four patients. Glucarpidase was administered at a dose of 50 U/kg for 15 and 4 patients, respectively in the two studies, and safety was analyzed for each of them.

RESULTS

The rate of CIR was 76.9% (95% confidence interval, 46.2-95.0%) in the CPG2-PII study. The median reduction rate of plasma MTX was 98.83% in the OP-07-001 study. Hypersensitivity, blood bilirubin increased, and headache for each patient were the only study drug-related events.

CONCLUSION

Glucarpidase showed an effect of reducing plasma MTX concentration in Japanese patients with DME as that observed in a previous US study, confirming its favorable safety and tolerability.

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.

Methotrexate toxicity treated with continuous venovenous hemofiltration, leucovorin and glucarpidase

High-dose methotrexate (MTX) can produce acute kidney injury, impairing MTX elimination. Continuous venovenous hemofiltration (CVVH) may enhance elimination in this setting, although its use is largely unstudied. A 79-year-old man received IV MTX for central nervous system lymphoma, and over a 34-h period his serum creatinine increased from 1.09 to 2.24 mg/dL. His serum MTX concentration (sMTX) at the end of this time period was 59.05 µmol/L. After urinary alkalinization and leucovorin and glucarpidase (CPDG₂) treatment, sMTX decreased. Fluid overload ensued and CVVH was initiated. The initial MTX extraction ratio and clearance were 0.22 and 47.0 mL/min, respectively. No MTX extraction occurred at an sMTX of 0.15 µmol/L. Continuous venovenous hemodialysis was initiated, and sMTX further declined. CVVH may help eliminate MTX and provide renal replacement at moderate sMTX.