OBJECT: Direct delivery of chemotherapeutic agents for the treatment of brain tumors is an area of focus in the development of therapeutic paradigms because this method of delivery circumvents the blood-brain barrier without causing adverse systemic side effects. Few studies have investigated longitudinal tumor response to this type of therapy. In this study, the authors examined the time course of tumor response to direct delivery of a chemotherapeutic agent in a rodent malignant glioma model. METHODS: To visualize tumor response to chemotherapy, the authors used bioluminescence imaging in a rodent model. Rat 9L gliosarcoma cells expressing a luciferase gene were inoculated into adult male rat striata. Ten days following surgery the animals were randomly divided into 4 groups. Groups 1 and 2 received 20 and 40 microl carboplatin (1 mg/ml), respectively, via convection-enhanced delivery (CED); Group 3 received 60 mg/kg carboplatin intraperitoneally; and Group 4 received no treatment. Tumor growth was correlated with luminescence levels twice weekly. RESULTS: Differential growth curves were observed for the 4 groups. Systemically treated rats showed decreasing photon flux emission at 15.0 + or - 4.7 days; rats treated with 20- or 40-microl CED showed decreased emissions at 4.0 + or - 2.0 and 3.2 + or - 1.3 days after treatment, respectively. Histopathologically, 6 of 12 CED-treated animals exhibited no residual tumor at the end point of the study. CONCLUSIONS: Direct and systemic delivery of carboplatin was examined to determine how the method of drug delivery affects tumor growth. The present report is one of the first in vivo studies to examine the time course of tumor response to direct drug delivery. The results indicate that direct drug delivery may be a promising option for treating gliomas.