A Canadian study conducted at Princess Margaret Hospital and the University of Toronto found significantly more memory and language difficulties in women who were receiving chemotherapy at the time of the study than in cancer-free control patients. The problem hasn't been well studied in the past because cognitive functioning is harder to measure than such physical side effects as nausea and vomiting. The study also found that women who had completed a course of chemotherapy at least a year before testing still had lingering problems with language and visual-motor skills, although, in the present study, the differences were not statistically significant compared to control patients. However, the finding is consistent with the study results of a Dutch group of investigators that showed persistent cognitive changes in women at an average of two years after receiving chemotherapy. In the Toronto study, patients receiving chemotherapy scored a median of 37 on a test of six cognitive functions, compared to 34.5 for patients who had completed chemotherapy, and 26 for control patients.
Higher scores represent poorer cognitive functions.
The study found that cognitive decline was not explained by differences in age, educational level, menopausal status, or mood. When those variables were considered, cognitive differences between the control group and women receiving chemotherapy still remained significant. A larger follow-up study is being conducted to provide more information about mechanisms that could lead to this cognitive decline. While it seems most likely that cognitive changes are due to direct effects of the anti-cancer drugs on the brain, effects produced by hormonal changes or by other medications commonly used with chemotherapy may also play a role.