A longitudinal study of the effects of chemotherapy on cognitive functioning in breast cancer
Breast cancer patients who receive chemotherapy frequently report observing a decline in cognitive functioning, otherwise termed "chemobrain." Extant research has suggested potential adverse effects of chemotherapy on cognitive functioning. The majority of studies have investigated the short-term effects on cognitive functioning, assessing participants within two years post-chemotherapy treatment. Very few studies have assessed for potential late effects of chemotherapy on cognitive functioning. Prospective, longitudinal studies are best equipped to answer the question of late effects of chemotherapy on cognitive functioning. To date, all prospective, longitudinal studies have assessed patients within one year of chemotherapy completion. In addition, while studies have failed to demonstrate a relationship between patient reports of cognitive functioning and performance on objective measures of cognition, no study has assessed the relationship between informant reports and patients’ performance on objective measures. Research with other groups has demonstrated a relationship between informant report and patient performance. This study was conducted with the purpose of clarifying the late effects of chemotherapy on cognitive functioning, using a prospective, longitudinal design. A second goal was to assess the accuracy of informant report on cognitive functioning. A total of 26 breast cancer patients that were previously assessed at baseline (pre-chemotherapy) and a short-term (approximately 7 months) follow-up were recruited to participate in this long-term assessment. Participants were administered the same comprehensive neuropsychological battery. Self-report scales of emotional well-being, quality of life, fatigue, and subjective reports (patient and informant) were also included. To reduce concerns of experiment-wise error, three domains (executive functioning, psychomotor speed, and verbal memory) that demonstrated the largest effect sizes in a recent meta-analysis were chosen as primary cognitive variables. The other four variables were examined as exploratory variables. Repeated Measures 2 (Group) by 3 (Time) MANOVAs were conducted to test the hypothesis of differential effects of treatment on cognition over time. While there was modest evidence of a negative short-term effect of chemotherapy on executive functioning, there was no evidence of any negative long-term effects of chemotherapy on any measure of cognitive functioning. All participants tended to demonstrate improved performance over time. While informants tended to report fewer cognitive problems than patients did themselves, the hypothesis that informant reports would correlate with patients’ performance on objective measures was also not supported. The results found for both aims might be explained in part by the low power in this study. Other possible suggestions for these results and suggestions for future research are discussed.^
Silvia Bigatti, Purdue University.