Treatment of primary central nervous system lymphoma with induction of complement‐dependent cytotoxicity by intraventricular administration of autologous‐serum‐supplemented rituximab

We describe an immunocompetent 19-year-old man with CD20-positive primary central nervous system (CNS) lymphoma refractory to chemotherapy and irradiation. After intraventricular administration of rituximab, a chimeric anti-CD20 monoclonal antibody, supplemented with autologous serum, a remarkable response developed to the CNS parenchymal lymphoma. Cytotoxicity assays showed that untreated patient's serum with rituximab, but not that of heat-inactivated patient's serum with rituximab or rituximab alone, induced potent rituximab-mediated cytotoxicity against tumor cells in the patient's cerebrospinal fluid, suggesting induction of complement-dependent cytotoxicity against CNS lymphoma.