Disseminating Necrotizing Leukoencephalopathy Associated With Intra-CSF Methotrexate Chemotherapy: A Retrospective Observational Study.

BACKGROUND AND OBJECTIVES: Leptomeningeal metastases (LMs) are neoplasms that proliferate to membranes lining the brain and spinal cord. Intra-CSF methotrexate (MTX) chemotherapy is a prevalent treatment option. However, resultant long-term neurotoxicity can lead to irreversible disseminated necrotizing leukoencephalopathy (DNL). This study aims to determine the incidence, characteristics, risk factors, and outcomes of DNL following intra-CSF MTX chemotherapy for LM.

METHODS: We retrospectively reviewed patients with LM who received intra-CSF MTX between 2001 and 2021 at the National Cancer Center of Korea. Patients with a follow-up duration of <3 months and those without follow-up MRI after MTX administration were excluded. The primary outcome was the development of DNL, evaluated based on the clinical and radiologic definitions of DNL. Logistic and Cox proportional regression models were used to assess the risk of DNL in patients with LM receiving intra-CSF MTX chemotherapy.

RESULTS: Of the 577 patients included in the DNL investigation, 13 (2.3%) were identified to have irreversible DNL. The MRI features of DNL typically include necrotic changes in the bilateral anterior temporal region, extensive white matter, and/or brainstem lesions. All patients with DNL experienced fatal clinical course despite MTX cessation. Logistic regression analysis revealed that a cumulative dose of MTX significantly affected DNL occurrence. Multivariable analysis showed that the factor of ≥10 MTX rounds was significant for DNL development after adjusting for route of MTX administration and prior brain radiotherapy (odds ratio 7.32, 95% CI 1.42-37.77 at MTX rounds ≥10 vs < 10). In the Cox proportional hazards model considering time to occurrence of DNL, ≥10 rounds of MTX were identified as an independent predictor of DNL (hazard ratio 12.57, 95% CI 1.62-97.28, p = 0.015), even after adjusting for the synergistic effect of brain radiotherapy.

DISCUSSION: DNL is a rare but fatal complication of intra-CSF MTX chemotherapy, and its progression cannot be prevented despite early recognition. The cumulative dose of intra-CSF MTX was an independent risk factor for DNL occurrence. Thus, intra-CSF MTX treatment for patients with LM should be administered with caution considering the possibility of the cumulative irreversible neurotoxicity.