Efficacy after sequencing of brain radiotherapy and enhanced antibody targeted chemotherapy delivery in a rodent human lung cancer brain xenograft model.

Abstract

The objective of this study was to evaluate the efficacy of sequencing radiation therapy (RT) and antibody targeted chemotherapy (BR96-DOX) in nude rats bearing human lung cancer (B.5 LX-1) intracerebral (i.c.) xenografts. Our approach was to administer RT using 20 Gy single-fraction cranial irradiation either before, concurrent with, or after BR96-DOX treatment via osmotic blood-brain barrier disruption to enhance immunoconjugate delivery. All rats were inoculated with i.c. B.5 LX-1 tumors and were randomly assigned to treatment groups. BR96-DOX alone on Day 6 or Day 12 significantly increased survival compared to negative control rats receiving no treatment (25.9 +/- 2.1 and 23.3 +/- 2.5 days vs. 14.8 +/- 1.9 days, p < 0.05). Rats that received chemotherapy before radiation (34.0 +/- 2.0 days) lived the longest compared to the other sequences (RT prior, 29.5 +/- 1.9; RT concurrent, 27.1 +/- 2.1). Histopathology of 39 rat brains did not reveal any neuropathology. Enhanced delivery of immunoconjugates is more effective in combination with RT for the treatment of experimental metastatic brain tumors. Moreover, BR96-DOX administration prior to RT significantly increased survival compared to those receiving RT and chemotherapy concurrently (p < 0.05).