Radioimmunotherapy targeting the extra domain B of fibronectin in C6 rat gliomas: a preliminary study about the therapeutic efficacy of iodine-131-labeled SIP(L19)

Despite aggressive treatment protocols, patients suffering from glioblastoma multiforme still experience poor outcome. Therefore, new adjuvant therapeutic options such as radioimmunotherapy (RIT) have been studied and have resulted in significant survival benefit. In this study, we assessed the efficacy of a novel radioimmunotherapeutic approach targeting the extra domain B (EDB) of fibronectin, a marker of angiogenesis, in glioma-bearing rats. Methods: C6 gliomas were induced intracerebrally in Wistar rats. Ten to 11 days later, 220-360 MBq of iodine-131-labeled anti-EDB SIP(L19) ("small immunoprotein") was administered intravenously into nine animals, yielding a radiation dose of 13-21 Gy. Another nine rats served as controls. Then the following parameters were compared: median survival time, tumor size and histology. Results: Histological examination of the tumors revealed typical glioblastoma characteristics. Eleven of 18 rats developed a tumor size bigger than 150 mm³. When these animals were used for survival analysis, median survival did significantly differ between groups [22 days (therapy; n=7) vs. 16 days (control; n=4); P<.0176]. Conclusions: In this preliminary trial, ¹³¹I-SIP(L19)-RIT showed promising potential in treating C6 gliomas, warranting further studies. However, larger trials with preferentially higher doses are needed to confirm this finding and, potentially, to further increase the efficacy of this treatment.