NIMG-38. RECOGNIZING DISSEMINATED NECROTIZING LEUKOENCEPHALOPATHY IN LEPTOMENINGEAL CARCINOMATOSIS PATIENTS TREATED WITH INTRATHECAL METHOTREXATE VIA OMMAYA RESERVOIR AFTER WHOLE BRAIN IRRADIATION

Abstract

Abstract BACKGROUND Disseminated necrotizing leukoencephalopathy (DNL) is a rare complication of intrathecal (IT) methotrexate administration with a previously reported incidence of 2.8%1 in patients undergoing treatment for central nervous system leukemia or lymphoma. The purpose of this study is to estimate the incidence of DNL in a series of patients undergoing treatment for leptomeningeal carcinomatosis (LMC) and to better characterize the radiographic findings associated with DNL. METHODS A retrospective review of a prospectively gathered database of 36 LMC patients was conducted. Patients were treated with whole brain radiation and a standardized regimen of twice-weekly IT methotrexate in the context of an established IT chemotherapy clinic. Data regarding the patients’ primary cancer pathology, time from initiation of IT methotrexate to onset of DNL, and radiographic characteristics of DNL were collected. RESULTS Six of 36 patients (16.7%) developed DNL. Mean time from initiation of IT treatment to development of DNL was 6.7 months. Primary pathologies of the DNL patients were breast (3), melanoma (1), GI (1), and pancreatic neuroendocrine (1). Radiologic presentation included areas of T2 hyperintensity, T1 hypointensity with contrast-enhancement, and restricted diffusion, all consistent with acute demyelination. These radiographic changes predominantly involved the catheter tract, periventricular and deep white matter, and grey-white interface. Interpretation of the magnetic resonance imaging by radiologists was highly inaccurate with the findings interpreted as catheter infection, progression of metastatic disease, stroke, or “possible treatment effect”, but never correctly identified as DNL. CONCLUSION DNL is a rare complication of intrathecal chemotherapy but may have a higher incidence in patients undergoing aggressive management of LMC than in those being treated for central nervous system lymphoma or leukemia. Although the imaging in DNL often exhibits characteristic findings, the rarity of this pathology leads to frequent misinterpretation, potentially complicating management of LMC.