Background. Intralesional radioimmunotherapy (RAIT) may improve the management of malignant gliomas whose prognosis is, at present, very poor. Current treatment modalities (e.g., surgery, radiotherapy, and chemotherapy) may prolong survival by a few months but cannot prevent tumor recurrence. Methods. Following one or more surgical operations, radiotherapy, and chemotherapy, 24 patients with recurrent malignant gliomas (23 brain and 1 spinal cord) underwent RAIT with 2 murine monoclonal antibodies (MoAb), BC‐2 and BC‐4, raised against tenascin (TN). This antigen is expressed in large amounts in the stroma of glial tumors but not in normal brain tissue. The isotope used was iodine‐131 (131I). The radiolabelled antibodies were injected directly into the tumor by means of a removable catheter or an indwelling catheter placed in the site of disease at the time of craniotomy. The patients were admitted to the protocol if histochemical analysis of their tumors demonstrated the presence of TN in high abundance. Biodistribution and dosimetry of an intralesional tracer dose (1 mg MoAb and 37 MBq 131I) were studied. RAIT was performed by the administration of escalating doses of radioiodine, ranging from 15 mCi to 57 mCi. In many cases, RAIT was was repeated two, three, or four times (on 8, 3, and 4 patients, respectively). Results. Pharmacokinetic data resulted, on average, as follows: the 24‐hour tumor/background ratio was 16.6; the percentage of injected dose concentrated per gram of tumor at 24 hours was 2.4%; and the effective half‐life of the MoAb at the tumor was 74.5 hours. The mean radiation dose to the tumor was 36.48 cGy per MBq of 131I injected. Both systemic and brain toxicities were absent, while human anti‐mouse antibody production after MoAb administration occurred in only a few cases. At present, 17 patients are assessable, with a median survival time of 16 months. Objective responses consisted of 5 tumor stabilizations (median time, 9 months), 3 partial remissions (11 months), and 3 complete remissions (15 months). Cancer 1994; 73:1076‐82.

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 (greater than 50% reduction in tumour volume; PR) and I complete remission (CR). One patient with PR relapsed after II months; the other 2 patients were still maintaining their responses at the time of writing, 17 (CR) and 12 (PR) months after injection.

The high-grade malignant gliomas (anaplastic astrocytomas and glioblastoma) have a very bad prognosis since the available methods of treatment (surgery, radiotherapy and chemotherapy) are unable to control the progression of the disease for long. The use of specific monoclonal antibodies labelled with a suitable isotope (iodine-131 or yttrium-90) represents an effective approach to hamper tumour regrowth. Some authors have injected the antibodies intravenously, or have tried to increase the tumour/background ratio with the avidin/biotin system. In many cases the labelled monoclonal antibodies were injected directly into the tumoral bed after the operation. The authors' experiences concern a quite large locoregional radioimmunotherapy study which was performed by using antitenascin antibodies labelled initially with 131I and more recently with 90Y. The clinical results demonstrate the ability of this technique to control, for a long time, the growth of these tumours. The glioblastoma median survival was prolonged to 25 months (131I group) or 31 months (90Y group). The response rate (which comprises PR, CR and NED) was 47.1% (glioblastoma 131I group) or 40% ( glioblastoma 90Y group). In many cases a significant tumour shrinking effect was radiologically demonstrated. The use of 90Y proved more favourable in bulky lesions, and reduced the radioprotection problems.

CONCLUSIONS.In selected patients, locoregional radioimmunotherapy can be included in a multimodal strategy to control high grade malignant gliomas and produce favorable results.

Thirty patients with recurrent glioblastomas (29 brain, 1 spinal cord) received intralesional radioimmunotherapy aiming to control the progression of the tumor after surgery and radiotherapy. The BC-2 and/or BC-4 murine MAbs (Sorin-Biomedica, Saluggia, Italy) were utilized. They strongly react against tenascin (TN), which is an extracellular antigen expressed in large amounts by the stroma of glioblastoma but not by normal brain. The MAbs were labeled with I-131 and were injected directly into the tumor mass to maximize the antibody concentration in the tumor and to irradiate the neoplastic cells. The dose consisted, on average, of 3 mg antibody and 1100 MBq I-131. In most cases the radioimmunotherapy (RIT) applications were repeated two, three, or four times. No systemic adverse reactions were recorded. The brain tolerance to direct antibodies injection was quite good. The antibody concentration in the tumor was high and the MAb residence time in neoplastic tumor was prolonged. Consequently the mean radiation dose to the tumor was high: > 25,000 cGy/cycle. Of 23 evaluable patients, we recorded 7 tumor stabilization (lasting, on mean, 9.1 mo), 4 partial remission (10 mo), and 4 complete remission (18 mo). The overall response rate was 34.7%.