TREATMENT OF RECURRENT AND CYSTIC MALIGNANT GLIOMAS BY A SINGLE INTRACAVITY INJECTION OF I-131 MONOCLONAL-ANTIBODY - FEASIBILITY, PHARMACOKINETICS AND DOSIMETRY

A pilot study was undertaken to determine the feasibility of infusing I-131 labelled monoclonal antibodies (MoAbs) into either the cavity remaining after resection of malignant glioma or into glioma cysts. Of the seven patients recruited into the study, two had cystic lesions and five resection cavities. Six of the seven were treated after relapse from primary therapy. All patients apart from one, were given a single injection of I-131 conjugated to a MoAb (ERIC-1) recognising the human neural cell adhesion molecule (NCAM). One patient received a further injection of I-131-MoAb after regrowth of their disease. Pharmacokinetic studies revealed that the MoAb remained predominantly in the tumour cavity with little leakage into the systemic compartment. This resulted in a high calculated dose of radiation being delivered to the tumour cells either lining or within close proximity to the cavity/cyst wall. In such a small study, it is not possible to determine accurately response rates, but individual patient responses were observed. This, along with the low toxicity noted, demonstrates the feasibility of using I-131-MoAbs in this way. With I-131, radiation dose is deposited in tissue to a depth of 1 mm from the source. The possibility of applying isotopes such as Yttrium-90 which will irradiate tumour/tissue to a greater depth (6 mm) is discussed in context with the biology of glioma infiltration into normal brain parenchyma.