Immunotoxin therapy.

Immunotoxins are extremely potent agents that recognize specific antigens located on metastatic tumor cells and cause cytotoxicity after cell entry by inhibiting protein synthesis. These agents have considerable in vitro efficacy against numerous metastatic tumor cell lines. In vivo studies have shown complete tumor regression in athymic animals bearing flank tumors or with leptomeningeal neoplasia. Phase I clinical trials have demonstrated therapeutic efficacy in patients with carcinomatous meningitis or with intraparenchymal brain metastases. These agents may be particularly appropriate for patients with widespread intracranial metastatic disease or with radioresistant tumor histology.