title: Imaging of central nervous system lymphomas with iodine-123 labeled rituximab.
abstract: Most patients with primary central nervous system (CNS) lymphoma (PCNSL) relapse after initial response to chemotherapy or the combination of chemotherapy and irradiation. Thus, novel treatment regimens for relapsed PCNSL are needed. As the majority of PCNSL are B-cell neoplasms expressing the CD20 antigen, treatment with the chimeric monoclonal antibody (MAb) rituximab might be reasonable. Nevertheless, the potential efficacy of intravenous rituximab in PCNSL seems to be limited as MAbs are high molecular weight proteins, which might be unable to pass the blood brain barrier. Thus, we performed dosimetric measurements with iodine-123 (123I)-rituximab to evaluate rituximab uptake in PCNSL after systemic intravenous administration. We analyzed four patients with PCNSL receiving a preinfusion of 250 mg/m2 rituximab followed by 200-500 MBq of the gamma-emitter 123I-rituximab. Single photon emission computed tomography (SPECT) was performed 1, 24 and 48 h after administration of the radio-immunoconstruct. Only one patient showed a very weak or questionable uptake of 123I-rituximab into tumor tissue which was ninefold lower compared with the blood-pool accumulation. These data suggest that systemic MAb-based radio-immunotherapy is not feasible in patients with PCNSL because a sufficient activity in the tumor will be associated with severe hematotoxicity. If an uptake of therapeutic rituximab doses into PCNSL can be achieved remains questionable.
authors.affiliation: Department of Nuclear Medicine, University of Cologne, Cologne, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Dietlein
authors.forename: Hendrik
authors.initials: H
authors.lastname: Pels
authors.forename: Holger
authors.initials: H
authors.lastname: Schulz
authors.forename: Oliver
authors.initials: O
authors.lastname: Staak
authors.forename: Peter
authors.initials: P
authors.lastname: Borchmann
authors.forename: Klaus
authors.initials: K
authors.lastname: Schomäcker
authors.forename: Thomas
authors.initials: T
authors.lastname: Fischer
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Eschner
authors.forename: Elke
authors.initials: E
authors.lastname: Pogge von Strandmann
authors.forename: Harald
authors.initials: H
authors.lastname: Schicha
authors.forename: Andreas
authors.initials: A
authors.lastname: Engert
authors.forename: Roland
authors.initials: R
authors.lastname: Schnell
mesh_terms: D000328:Adult; D000368:Aged; D000911:Antibodies, Monoclonal; D058846:Antibodies, Monoclonal, Murine-Derived; D001932:Brain Neoplasms / Q000000981:diagnostic imaging*; D006801:Humans; D007457:Iodine Radioisotopes; D016393:Lymphoma, B-Cell / Q000000981:diagnostic imaging*; D016403:Lymphoma, Large B-Cell, Diffuse / Q000000981:diagnostic imaging*; D016719:Radioimmunodetection; D000069283:Rituximab; D015899:Tomography, Emission-Computed, Single-Photon
chemical_list: D000911:Antibodies, Monoclonal; D058846:Antibodies, Monoclonal, Murine-Derived; D007457:Iodine Radioisotopes; D000069283:Rituximab