Use of the extracorporeal detoxification methods for methotrexate elimination

The article considers a clinical case of a 12-year-old child with osteosarcoma of the left tibia, T1N0M0G3, treated with high-dose methotrexate 12 g/m2. As a result of delayed elimination of methotrexate, the patient developed acute liver failure. The ALT level increased to 4790 U/L, AST — to 4320 U/L, which indicates life-threatening acute liver damage. There was no coagulopathy, significant increase in bilirubin, and hepatic encephalopathy. The timely use of efferent therapy allowed avoiding the complete course of acute liver failure. The patient received intravenous hydration therapy and urine alkalinization with 3000 ml/m2/day of 5% glucose in combination with 20 μmol NaHCO3/L and 20 μmol KCl/L. The urine output was more than 600 ml/m2/6 hours. Additionally, antidote therapy with calcium folinate was administered. In this case, we used continuous venous-venous hemodiafiltration using Prismaflex. After the first session, which lasted for 78 hours, there was a re-increase in serum methotrexate concentration and ALT, AST levels, which indicates a large volume of distribution of methotrexate and the need for long-term extracorporeal therapy. Therefore, the second session of continuous venous-venous hemodiafiltration was provided. After the second session, there was no re-increase in methotrexate level in the blood and the transaminases and total bilirubin returned to normal levels. Additionally, the patient was tested for homocysteine levels for hyperhomocysteinemia, as well as 4 genes that also determine the predisposition to hyperhomocysteinemia — methylenetetrahydrofolate reductase gene MTHFR C677T, A1298C, methionine synthase MTRR, and MTR. The presence of elevated levels of homocysteine, as well as heterozygosity of these genes, indicate a slow excretion of methotrexate or a complete delay in its excretion. Our patient presented the negative results of these tests. Conclusions. This clinical case indicates the effectiveness of continuous venous-venous hemodiafiltration in combination with intravenous hydration, urine alkalinization, and antidote therapy in the treatment of hepatotoxicity of high-dose methotrexate on the background of delayed excretion.