Association of chemotherapy and subjective cognitive impairment in breast cancer patients: Meta-analysis of longitudinal prospective cohort studies

Purpose: This meta-analysis with longitudinal prospective cohort studies aimed to (a) determine whether chemotherapy is associated with time-dependent subjective cognitive impairment outcomes in breast cancer patients, and (b) identify the time point with the highest impact of chemotherapy on subjective cognitive impairment. Methods: Data were gathered from PubMed, EMBASE, CINAHL, PsycInfo, and the Cochrane Library. The mean differences of the subjective cognitive impairment level between the chemotherapy-treated patients and controls (patients not treated by chemotherapy and healthy subjects) were calculated using effect sizes (Hedges' g) by clinical time periods. The five clinical time periods were (a) baseline, (b) during chemotherapy, (c) within 1 month postchemotherapy, (d) within 1 year postchemotherapy, and (e) 1 year or longer postchemotherapy. Results: Longitudinal data from nine data sets from 13 studies were pooled and analyzed. At baseline, chemotherapy-treated patients showed slightly better subjective cognitive impairment compared to patients not treated by chemotherapy and did not differ from healthy controls. Yet, the chemotherapy-treated patients had significantly worse subjective cognitive impairment compared to both type of controls after initiating chemotherapy. The effect sizes for the group differences were larger for the group comparison with healthy controls than the nonchemotherapy control (-0.50 vs.-0.19). The largest effects were found within 1 month post chemotherapy (-0.85), suggesting the acute impact of chemotherapy. Conclusions: Chemotherapy is associated with subjective cognitive impairment. The impact of chemotherapy appears to be an acute rather than a chronic side effect. Clinicians must consider including the assessment and management of subjective cognitive impairment in their routine practice.