tokens: In the nine responders , median duration of chemotherapy response from the time of operation was 25 weeks ( range 12 to more than 91 weeks ). The median duration of survival in the 12 patients was 54 weeks ( range 21 to more than 156 weeks ), with an 18 - month survival rate of 42 %. Twenty - four patients with recurrent Grade I to IV astrocytomas , whose resection and irradiation therapy had failed , received two to eight courses of intra - arterial BCNU therapy .