High-Dose Methotrexate-Induced Renal Dysfunction: Is Glucarpidase Necessary for Rescue?

Abstract

TO THEEDITOR: Widemann et al 1 report the use of glucarpidase, leucovorin, and thymidine for high-dose methotrexate-induced renal dysfunction. When patients develop delayed excretion of methotrexate and impaired renal function after the administration of high-dose methotrexate there are two equally important imperatives. First, we must protect the patients from the potential toxicity of prolonged exposure to the antifolate drug methotrexate. Potential toxicities include myelosuppression, mucositis, and hepatoxicity, and can be lethal. The second imperative is to have the patient’s renal function return to normal to allow continuation of the chemotherapy needed to treat the underlying malignancy. The authors performed an analysis to determine which factors predicted greater than or equal to grade 4 toxicity. They noted that inappropriate increase in leucovorin predicted perfectly for development of greater than or equal to grade 4 toxicity and therefore could not be included in their multiple factor logistic regression analysis. We have reported our experience treating patients who have delayed methotrexate excretion and renal failure after high-dose methotrexate administration using high-dose leucovorin as the sole form of rescue. 2 All patients in our experience were salvaged. None of our patients died. The authors report that the median time to recovery of renal function for their cohort was 22 days. Our experience, albeit considerably smaller, achieved at least as good a time to recovery of normal renal function. One possible interpretation of the results that the authors report is that glucarpidase was not an essential component of rescue for patients experiencing high-dose methotrexate-related renal dysfunction and that similar results could have been achieved with the use of high-doses of leucovorin alone. Glucarpidase is unquestionably an excellent way to lower the plasma methotrexate concentration. This effect, however, has no impact on intracellular concentrations of methotrexate or on renal function. Protection of cells from intracellular methotrexate still requires the administration of high-doses of leucovorin and renal recovery appears to take place independently of glucarpidase administration. The authors’ conclusion that early intervention with the combination of leucovorin and glucarpidase is highly effective in patients who develop high-dose methotrexate-related renal dysfunction may be true but the authors should consider the possibility that similar results could be achieved with leucovorin alone.