Action and efficacy of p-[131I]iodo-L-phenylalanine on primary human glioma cell cultures and rats with C6-gliomas.

BACKGROUND Recently we demonstrated high selectivity and long retention of p-[123I]iodo-L-phenylalanine (IPA-123) for diagnostic purposes in gliomas. Here we describe the potency of the iodine-131-labelled analogue p-[131I]iodo-L-phenylalanine (IPA-131) for experimental treatment of gliomas. MATERIALS AND METHODS Two human glioma cell cultures and 15/20 rats with C6-gliomas were exposed to IPA-131. RESULTS After 24-h-exposure the cell number of the glioma cell cultures was reduced by 77% and 79%, respectively. Four out of five untreated rats died 8-24 days after implantation and had verifiable tumours. Seven animals died despite therapy, while 8 were soon healthier, gained body weight and were sacrificed 81 days after implantation, at which time survival of the treated animals was significantly prolonged (p < 0.05). At autopsy, instead of tumours there were substance defects, surrounded by pre-existing parenchyma infiltrated by probable tumour cells that were not discernible from reactive astrocytes, lymphocytes, monocytes and multinuclear giant cells. CONCLUSION IPA-131 has promising activity against human glioma cells in vitro and experimental gliomas in vivo.