Neoplastic meningitis from a pineal tumour treated by antibody-guided irradiation via the intrathecal route.

A monoclonal antibody (UJ181.4) was labelled with 131I and given intrathecally to a patient who was critically ill with neoplastic meningitis due to a disseminated pineoblastoma. The target antigen had first been demonstrated on tumour cells by immunocytological testing of cerebrospinal fluid (CSF). As a preparation for therapy, a test dose of 131I-UJ181.4 antibody was given simultaneously with a control antibody labelled with 125I. Good evidence of in vivo immunolocalization was obtained by external gamma counting and by analysis of the radiolabels on centrifuged CSF cells. Specificity ratios of between 10:1 and 20:1 were obtained by these methods. A single relatively small therapeutic dose of 131-I (870 MBq) given by the intrathecal route, resulted in a marked clinical improvement and sustained remission for 22 months.