Tumor resection cavity administered iodine-131-labeled antitenascin 81C6 radioimmunotherapy in patients with malignant glioma: neuropathology aspects

Abstract Introduction The neurohistological findings in patients treated with targeted β emitters such as131 I are poorly described. We report a histopathologic analysis from patients treated with combined external beam therapy and a brachytherapy consisting of a131 I-labeled monoclonal antibody (mAb) injected into surgically created resection cavities during brain tumor resections. Methods Directed tissue samples of the cavity walls were obtained because of suspected tumor recurrence from 28 patients. Samples and clinical follow-up were evaluated on all patients (Group A) based on total radiation dose received and a subset of these ( n =18; Group B, proximal therapy subset) who had received external beam therapy within ≤3 months of mAb therapy and undergoing 26 biopsies over 37 months. Histologic outcomes were “proliferative glioma,” “quiescent glioma” and negative for neoplasm. Statistical analysis was used to assess the casual relation between total absorbed dose (131 I-mAb+external beam) and histologic diagnosis. Results The lesions observed after131 I-mAb therapy were qualitatively similar to those reported for other types of radiation therapy; however, the high localized dose rate and absorbed doses produced by the short range of131 I β particles seem to have resulted in an earlier necrotic reaction in the tumor bed. Among all 28 (Group A) patients, median survival from tissue analysis after mAb therapy depended on histopathology and total radiation absorbed dose. Median survival for patients with tissue classified as proliferative glioma, quiescent glioma and negative for neoplasm were 3.5, 15 and 27.5 months, respectively. Without categorization, total dose was a significant predictor of survival ( P