The Effects of Chemotherapy on Cognition in Women with Breast Cancer

Abstract

Advances in cancer treatment have led to increasing numbers of survivors left to struggle with the long-term adverse effects of disease and treatment. Many possible effects have been described including anxiety, depression, as well as physical side effects and consequences of cancer treatment. One particular adverse effect that is frequently reported but often overlooked in clinical practice is disturbances of cognitive functioning. Cancer-related cognitive impairment (CRCI) is a growing area of research with important clinical implications for current patients and survivors. Despite a huge increase in this research endeavour in the last 20 years, many important questions remain unanswered due, in large part, to methodological limitations of many of the studies. The overall goal of this dissertation is to critically examine previous CRCI research from a methodological perspective. It will explore limitations and confounds in this research and provide suggestions for improving future work. This dissertation is comprised of three manuscripts, a critical literature review and two original papers, addressing specific research questions. The first original paper addresses the disparity between the results of objective (performance-based) and subjective (self-report) measures of cognition that is typically observed in samples of cancer patients, using multilevel modeling to explore the hypothesis that this is due to failure to address measures of change over time. Despite negative findings, the methodological approach taken to this research question provided greater evidence for this subjective-objective disparity as well as methodological suggestions for future studies. The second original paper explores the sensitivity and validity of a computerized cognitive test for measuring CRCI to determine if it might be an appropriate alternative to traditional, resource-intensive neuropsychological testing. This study found that, although the computerized measure of cognitive functioning was not sensitive enough to detect changes at the individual level or within specific domains, it was sensitive to changes in cognitive functioning at the group level suggesting its usefulness as a screening tool in research settings. By addressing methodological limitations of research to date and, specifically, the two issues identified above, this dissertation aims to a) make recommendations to help improve the quality of future research, b) validate the cognitive complaints of cancer patients, and c) improve access to cognitive assessments leading to increased detection and treatment of cognitive side effects and improvement in quality of life of cancer survivors.