The Impact of sustained and intermittent docetaxel chemotherapy regimens on cognition and neural morphology in healthy mice

Rationale: A subset of cancer survivors demonstrates impairments in cognition long after chemotherapy completion. At present, it is unclear whether these changes are due to direct neurotoxic effects of chemotherapy. Objectives: This study examined the impact of variable docetaxel (DTX) chemotherapy dosing on brain DTX exposure via analyses of neural morphology and changes in cognition. Methods: Male CD-1 mice were treated with DTX either intermittently (8 mg/kg i.p. weekly) or via a sustained delivery system (DTX-PoLigel), which continuously releases DTX. Both groups received total DTX doses of 32 mg/kg. Mice were assessed on the novel object recognition (NOR) task and the Morris water maze (MWM) shortly after treatment. Results: Post-treatment behavioral testing demonstrated impaired NOR in mice treated with either dosing schedule relative to controls. No differences were observed between groups in MWM training and initial testing, though control mice performed better than chance while DTX-treated mice did not. Appreciable amounts of DTX were found in the brain after both treatment regimens. DTX treatment did not significantly increase levels of apoptosis within the CNS. However, some elevation in neural autophagy was observed following DTX treatment. Analysis of astrocytic activation demonstrated that intermittent DTX treatment resulted in an elevation of GFAP-positive astrocytes for 48 h after administration. Sustained chemotherapy demonstrated prolonged but lower levels of astrocyte activation over 9 days following implantation. Conclusions: DTX treatment induced cognitive impairment shortly after treatment. Further, these findings suggest an association between DTX dosing, neurotoxicity, and cognitive effects.