Inhibition of potentially lethal damage recovery by cisplatin in a brain tumor cell line.

Radiation resistant tumours such as gliomas show enhanced capacity for potentially lethal damage recovery (PLDR), which can be inhibited by cisplatin. The 9L rat brain tumour cell line, like human glioma cell lines, shows a large capacity for PLDR. Cisplatin administered at 6 micrograms/ml for 1 hour immediately following acute irradiation (18 Gy) is shown to cause significant inhibition of PLDR, while 3 micrograms/ml causes little inhibition. Cisplatin-radiation treatment sequence affects PLDR inhibition, with maximum effect seen when cisplatin is administered immediately after irradiation, during the period of rapid cellular recovery. These data suggest that optimum interaction between radiation and cisplatin treatments can be achieved by maximizing intratumoural cisplatin levels during the post-irradiation recovery period.