Toxicity associated with high-dose intravenous methotrexate for hematological malignancies

Intravenous high-dose methotrexate (HD-MTX) is a critical chemotherapeutic agent in hematological malignancies, however, data are lacking on how to predict and prevent toxicities such as kidney injury. We retrospectively analyzed 539 episodes of HD-MTX (≥1 g/m²) delivered to 144 patients for treatment of prophylaxis of CNS hematological malignancy across three Australian institutions and correlated risk factors with toxicity. Clinically relevant (CTCAE v4.03 grade 2-4) nephrotoxicity occurred on 36 (7%) occasions and was mostly grade 2. Multivariate analysis revealed that doses ≥6 g/m² (HR 5.02, 95%CI 1.46-17.2, p = 0.01) and interacting/nephrotoxic drugs (HR: 7.15, 91%CI: 2.18-23.512, p = 0.001) were the only factors associated with nephrotoxicity. 48-hour methotrexate level, hypoalbuminemia and increasing age were associated with prolonged clearance but not nephrotoxicity. Mucositis, liver dysfunction and cytopenias were transient and mild in most cases. We have demonstrated that the most common risk factors for nephrotoxicity are modifiable which may assist clinical decision-making when administering this important drug.