Background: Several small scale clinical trials indicated a possible relationship between chemotherapy administration and the increased risk of cognitive impairments in patients with breast cancer, but little information was available from large population-based cohort studies.
Methods: We studied 62,565 women who were diagnosed with stages I-IV breast cancer at age ≥65 years from 1991 through 2002 from 16 regions in the Surveillance, Epidemiology and End Results program who were free of cognitive impairments at diagnosis with up to 16 years of follow-up, and also studied 9752 matched cohort based on the propensity of receiving chemotherapy. The cumulative incidence of cognitive impairments was calculated and the time to event (cognitive impairments) analysis was conducted using Cox hazard regression model.
Results: Overall, patients who received chemotherapy were 8% more likely to have drug-induced dementia compared with those without chemotherapy, but that was not statistically significant after adjusting for patient and tumor characteristics (hazard ratio = 1.08, 95% confidence interval = 0.85-1.37). The risk of developing Alzheimer disease, vascular dementia, or other dementias was significantly lower in patients receiving chemotherapy except for cognitive disorder which was not significantly different between the 2 chemotherapy groups. The results were somewhat similar in the entire cohort and the matched cohort based on the probability of receiving chemotherapy.
Conclusion: There was no significant association between chemotherapy and the risk of developing drug-induced dementia and unspecified cognitive disorders. The risk of developing Alzheimer disease, vascular dementia, or other dementias was significantly lower in patients receiving chemotherapy. This study with long-term follow-up did not support the findings that chemotherapy was associated with an increased risk of late stage cognitive impairments.