Purpose: To investigate the ability of systemically delivered BCNU to enhance the activity of either systemically delivered irinotecan (CPT-11) or locally delivered camptothecin from a biodegradable polymer for treatment of an intracranial 9L gliosarcoma.
Methods: We used a single systemic dose of BCNU on treatment day 1 in combination with systemic doses of CPT-11 on treatment days 1-5 and 8-12 against an intracranial rat 9L gliosarcoma model implanted into female Fischer 344 rats. We also used the same systemic dose of BCNU given on treatment day 1, followed by a local dose of a 20% loaded camptothecin biodegradable polymer implanted on the same day.
Results: Two doses of CPT-11 (10 and 60 mg/kg) were delivered systemically against intracranial 9L. Neither dose showed an increase in survival compared to controls ( P>0.2 for 10 mg/kg and P=0.17 for 60 mg/kg). Systemic delivery of CPT-11 (10 mg/kg per day) in combination with systemic BCNU (15 mg/kg) did not show a significant effect on survival compared to systemic BCNU alone ( P>0.2), even at the maximally tolerated systemic dose of CPT-11 (60 mg/kg per day; P=0.06). The combination of systemic BCNU (15 mg/kg) and intracranial delivery of camptothecin (20% loaded polymer), however, significantly extended survival compared to systemic BCNU alone ( P<0.001) and compared to intracranial delivery of camptothecin alone ( P=0.01).
Conclusions: In a 9L gliosarcoma model, systemic delivery of CPT-11 showed no benefit in survival when delivered alone or in combination with systemic BCNU, because CPT-11 is unable to cross the blood-brain barrier in cytotoxic levels. When cytotoxic levels of a topoisomerase I inhibitor are delivered directly to the brain tumor via a biodegradable polymer, however, the systemic delivery of the alkylating agent BCNU significantly enhances the antitumor effects of camptothecin in a 9L gliosarcoma model.