A Meta-Analysis of the Neuropsychological Effects of Adjuvant Chemotherapy Treatment in Women Treated for Breast Cancer

ABSTRACT

Given the improvement in mortality rates associated with breast cancer, the importance of understanding the long-term neuropsychological consequences of chemotherapy is becoming increasingly vital. This study applies meta-analytic techniques to the scant literature on the relationship between contemporary adjuvant chemotherapy treatment for breast cancer and cognitive dysfunction as examined through neuropsychological indices. Seven studies (involving more than 300 participants) were selected from over 200 potential articles, based on three inclusion criteria: presence of breast cancer, administration of chemotherapy treatment, and use of neuropsychological tests. From these, nine treatment-control comparisons were used to generate 129 Hedge's d effect sizes across the cognitive domains of simple attention, working memory short- and long-term memory, speed of processing, language, spatial abilities, and motor function. Small to medium cumulative effect sizes, showing diminished cognitive function for chemotherapy treatment groups compared to control groups, were obtained for each of the eight cognitive domains. Overall, these results suggest that women who undergo adjuvant chemotherapy as treatment for breast cancer may experience subtle yet consequential cognitive decline.

ACKNOWLEDGEMENT

This research was made possible with the generous support of the Canadian Breast Cancer Foundation – Ontario chapter.

Notes

^a Column lists the neuropsychological tests and authors, where 1 = Ahles et al. (2002); 2 = Brezden et al. (2000); 3 = Schagen et al. (1999); 4 = van Dam et al. (1998; standard dose); 5 = van Dam et al. (1998; high dose); 6 = Wieneke & Dienst (1995); 7 = Castellon et al. (2004); 8 = Wefel et al. (2004; short-term); 9 = Wefel et al. (2004; long-term).

^b Refers to the total number of effect sizes generated across studies. For example, in the domain “simple attention” the 14 effect sizes comprise 8 from Trails A, 2 from a vigilance task, and 4 from digit span (see superscripts attached to each test). Note that some tests have multiple components (example D & ND would generate two effect sizes).

LTS = long-term storage; D = dominant; ND = non-dominant; RT = right; LT = left.

^a Column lists the cognitive domains and relevant studies included, where 1 = Ahles et al. (2002); 2 = Brezden et al. (2000); 3 = Schagen et al. (1999); 4 = van Dam et al. (1998; standard dose); 5 = van Dam et al. (1998; high dose); 6 = Wieneke & Dienst (1995); 7 = Castellon et al. (2004); 8 = Wefel et al. (2004; short-term); 9 = Wefel et al. (2004; long-term).

^b Column lists the number of studies included per cognitive domain. Some studies were removed to achieve homogeneity (number in parentheses); these were working memory, see studies 1, 6, 9; long-term memory, see 9; speed of processing, see 6, 9; language, see 6, 9.

^c Hedge's d-weighted pooled effect size.

^d Total number of subjects (experimental and control) per effect size.

^e Confidence interval.

^f Column lists the number of studies that would be required to change the results from significant to non-significant based on a d of .35, mid-way between a small to medium effect size.

*p < .05

**p < .005

***p < .0001.