New evidence shows that systemic chemotherapy for breast cancer or lymphoma can result in a significant decline in cognitive function.

This finding was revealed after researchers at the Dartmouth-Hitchcock Medical Center in Lebanon, New Hampshire, compared 35 breast cancer and 36 lymphoma survivors treated with systemic chemotherapy with 35 and 22 patients treated with surgery and radiation therapy, respectively. In all cases, the time since the last treatment was approximately 10 years.

Results showed that the patients who had systemic chemotherapy scored significantly lower than their counterparts on tests of verbal and working memory, and psychomotor functioning.

Even after adjusting for diagnosis, age, education level, depression, anxiety and fatigue, the association remained strong. The investigators also noted a significant correlation between the number of chemotherapy cycles, ranging from one to 17, and poor test scores.

Explanations for the brain function decline include the possibility that chemotherapeutic drugs can cross the protective blood–brain barrier and directly affect the brain, or that their breakdown products (metabolites) may be the cause. More research is needed (J Clin Oncol, 2002; 20: 485-93).