Background: Breast cancer survivors commonly experience cognitive problems following cancer and its treatment. Although prior research focused on chemotherapy-related cognitive impairment, newer studies suggest that some women also experience cognitive problems prior to chemotherapy and radiation treatments. Accordingly, factors besides cancer treatment may also influence breast cancer survivors' cognitive function. Physical fitness benefits cognitive function in healthy adults, and breast cancer survivors experience declines in fitness even prior to adjuvant treatment.
Aims: The study investigated the extent to which cardiorespiratory fitness (CRF) impacted cognitive function among post-surgery breast cancer survivors prior to chemotherapy and radiation treatment, and examined the potential psychological pathways for this relationship. The prospective effect of cognitive function on adherence to chemotherapy and radiation treatments was also evaluated.
Methods: Following cancer surgery but before chemotherapy or radiation treatments, stage I through IIIA breast cancer survivors (n = 90, ages 26 to 75) completed neuropsychological tasks of verbal memory (Hopkins Verbal Learning Test), verbal fluency (FAS), executive function (Trail-Making Test, n-back task), and sustained attention (Conners Continuous Performance Test) in the context of a larger observational study. They also underwent a graded cycle ergometry test to measure peak oxygen consumption (VO2peak), and reported their depressive symptoms (Center for Epidemiologic Studies Depression Scale), anxiety symptoms (PROMIS Anxiety Scale), and sleep problems (Pittsburgh Sleep Quality Index). Chemotherapy and radiation treatment adherence was measured by concordance with National Comprehensive Cancer Network (NCCN) standards as well as the number of treatment appointments that were missed/cancelled by the patient, using medical record data.
Results: CRF did not concurrently benefit performance on verbal fluency, executive function, and sustained attention tasks. Although women with better fitness had higher immediate verbal memory scores than those with poorer fitness, this relationship was no longer significant when controlling for age, education, cancer stage, medical comorbidities, and time since surgery. There were not fitness-related differences in depressive symptoms, anxiety symptoms, or sleep problems, which did not individually or collectively mediate the relationship between CRF and cognitive function. Few participants missed any appointments (n = 11) or received inadequate treatment by NCCN standards (n = 10). Women with poorer attentiveness (indexed by CPT omissions) following surgery were subsequently more likely to miss or cancel a treatment appointment compared to women with higher attentiveness (OR = 1.265, 95% CI = 1.008 to 1.587). However, those with poorer executive function (indexed by n-back RT cost) were less likely to miss or cancel an appointment than those with better executive function (OR = .014, 95% CI = .000 to .978), an unexpected finding. Women's post-surgery verbal memory and verbal fluency did not impact their appointment attendance.
Conclusions: There were not consistent, clear links between cognitive function, cardiorespiratory fitness, and chemotherapy/radiation adherence in this sample of relatively healthy, well-adjusted women following breast cancer surgery. Although physical fitness did not appear to benefit cognitive function in this study, breast cancer survivors gain many other health advantages from being physically fit throughout the disease continuum. Increased research focus on the post-surgery period will help to determine the underpinnings of pre-treatment cognitive dysfunction and decreased fitness, as well as characterize the relevance of these problems to clinical and real-world outcomes in breast cancer survivorship.