OBJECTIVES: To determine patterns of dementia diagnosis seen after chemotherapy treatment.
DESIGN: Using the linked Surveillance, Epidemiology, and End Results (SEER)-Medicare database, International Classification of Diseases, Ninth Revision (ICD-9) diagnoses of dementia occurring in the years after breast cancer diagnosis were examined.
SETTING: The SEER program collects information from population-based tumor registries in seven metropolitan areas (San Francisco and Oakland, Detroit, Atlanta, Seattle, Los Angeles County, San Jose and Monterey Counties, and the greater California area) and eight states (Connecticut, Iowa, New Mexico, Utah, Hawaii, Kentucky, New Jersey, and Louisiana).
PARTICIPANTS: Eighteen thousand three hundred sixty women diagnosed with Stage II, III, or IV breast cancer.
MEASUREMENTS: Using validated ICD-9 diagnoses of dementia, the occurrence of dementia and other cognitive impairment in the years after breast cancer diagnosis in women who received chemotherapy was compared with that of women who did not. To account for group differences, propensity score analysis was used to balance the differences in groups before treatment. Risk of dementia was calculated using Cox proportional hazards modeling.
RESULTS: There were significant differences at baseline between individuals who received and did not receive chemotherapy. In the first few years after breast cancer diagnosis, dementia was more common in women who had not had chemotherapy, probably reflecting group differences at baseline. In the longer term, diagnoses of dementia were more common in women who had chemotherapy treatment (hazard ratio=1.20, 95% confidence interval=1.08–1.33).
CONCLUSION: These findings suggest the possibility of severe cognitive changes associated with chemotherapy, particularly over the long term.