Chemotherapy and the Risk of Dementia in Korean Breast Cancer Patients

Objective: This study aimed to investigate whether chemotherapy increases the risk of dementia in breast cancer (BC) patients using a nationwide health insurance claims database in South Korea.Methods: We conducted a retrospective cohort study using the Korean Health Insurance Review and Assessment (HIRA) database from 2007 to 2021.We identified women aged 40 to 70 years who were newly diagnosed with BC and underwent surgery between 2009 and 2021.Patients were categorized into chemotherapy-exposed and unexposed groups, and we applied 1:1 propensity score matching to balance baseline characteristics.The hazard ratios (HRs) and subdistribution hazard ratios (SHRs) for dementia were estimated using a Cox proportional hazards model and a Fine and Gray's competing risk model, which accounted for death as a competing event.Results: A total of 46,886 patients with BC were included, with 22,427 in the chemotherapy group and 24,439 in the non-chemotherapy group.After propensity score matching, the adjusted HR for dementia was 0.826 (95% confidence interval [CI]: 0.532-1.280),and the adjusted SHR was 0.683 (95% CI: 0.422-1.104).Both models showed no statistically significant association between chemotherapy and dementia risk.Conclusion: In this nationwide cohort study, chemotherapy in BC was not associated with an increased risk of dementia.This suggests that chemotherapy may not be a risk factor for the long-term development of dementia in BC patients.