Objective:Chemotherapy significantly improved the survival of breast cancer,but also brings various symptoms and psychological distresses.Cognitive dysfunction was usually ignored.This study aimed to investigate the changes in cognitive function during chemotherapy and its influence on the quality of life in breast cancer patients.Methods:Female patients with newly diagnosed breast cancer have prospectively enrolled in this study.Participants investigated and completed questionnaires at four-time points:pre-chemotherapy(T1),post-chemotherapy(T2),6 months(T3)and 12 months(T4)after the completion of chemotherapy.The Functional Assessment of Cancer Therapy-Cognitive scale and the Functional Assessment of Cancer Therapy-Breast Cancer scale used was to assess the cognitive function and the quality of life,respectively.Data were analyzed using descriptive and repeated-measures analysis of variance statistics.Results:One hundred and eighty-three patients participated in the study and completed questionnaires at least 2 times.The mean score of cognitive function and the quality of life were significantly different at a different time point(P<0.05 for all).The trends of cognitive scores shown that the most serious damage of cognitive function appeared after beginning chemotherapy and followed by a slowly turn back after the completion of chemotherapy.The trend of the mean score of the quality of life after chemotherapy was similar to that of the cognitive score.The degree of cognitive dysfunction was significantly associated with the score of the quality of life at each time point after chemotherapy(P<0.05).Conclusion:Chemotherapy is closely associated with a cognitive impairment,which contributes to a significant decrease in the quality of life of patients with breast cancer.