Treatment of intracranial human glioblastoma by direct intratumoral administration of 131I-labelled anti-tenascin monoclonal antibody BC-2

Ten patients with bulky brain glioblastoma, recurring after surgery, radiotherapy or chemotherapy, underwent direct intralesional radioimmunotherapy (RIT) using a monoclonal antibody (MAb), BC-2, raised against tenascin and labelled with 131I. Tenascin, the BC-2-recognized glycoprotein, is an antigen expressed by the stroma of malignant gliomas but not by normal cerebral tissue. Preliminary studies in animals have demonstrated the ability of anti-tenascin radiolabelled MAbs to detect and reduce tumours. A mean MAb dose of 1.93 mg (corresponding to 551.3 MBq of 131I) was injected directly into the tumour by means of a stereotaxic technique. Both systemic and local toxicity were negligible. After 24 hr, average tumour BC-2 uptake was 4.9% per gram and its effective half-life in neoplastic tissue was 66.5 hr: a mean radiation dose to target tissue of 36.48 cGy per MBq of injected 131I was delivered. Normal brain tissue and the major organs were spared. Most patients underwent multiple injections, reaching a cumulative tumour radiation ranging from 7,000 to 41,000 cGy. RIT failed to achieve any result in 4 of the 10 patients; in 3, the disease was stabilized; in the remaining 3, CT scan or NMR revealed 2 partial remission (>50% reduction in tumour volume; PR) and I complete remission (CR). One patient with PR relapsed after 11 months; the other 2 patients were still maintaining their responses at the time of writing, 17 (CR) and 12 (PR) months after injection.