Cohorts of 3 patients each receive escalating doses of irinotecan IV over 90 minutes once weekly within 3 weeks after Gliadel wafer implantation. One course of treatment consists of 4 weeks of irinotecan and 2 weeks of rest. If 1 patient experiences dose limiting toxicity (DLT) at a dose level, an additional 3 patients are entered at that same dose level. If 2 patients experience DLT, the maximum tolerated dose (MTD) has been surpassed and a total of 6 patients are treated at the previous dose level. The MTD is defined as the highest dose in which no more than 1 of 6 patients experiences DLT.