Death from Alzheimer's disease among cancer survivors: a population-based study

Objective: To evaluate the risk of death from Alzheimer's disease among cancer survivors in a population-based setting.Methods: Within Surveillance, Epidemiology and End Results (SEER)-9 registries, cancer patients who were diagnosed between 1975 and 2016 have been reviewed. Observed/expected ratios for the risk of death from Alzheimer's disease were calculated for the overall group as well as for clinically defined subgroups. "Observed" is the number of observed deaths from Alzheimer's disease in the studied group, while "Expected" is the number of deaths from Alzheimer's disease in a demographically similar group within the US and within the same period.Results: The current study evaluates a total of 3,579,199 cancer patients (diagnosed between 1975 and 2016) within the SEER-9 registries. Among those patients, 25,894 patients (0.72%) have Alzheimer's disease as their cause of death. Among long-term cancer survivors (≥10 years), O/E ratio of death from Alzheimer's disease was 1.13 (1.12-1.15). Death from Alzheimer's disease seems to be particularly associated with older age at time of cancer diagnosis (O/E for patients ≥70 years: 1.29 [95% CI: 1.26-1.31] versus O/E for patients <70 years: 1.01 [95% CI: 0.98-1.03]), American Indian race (O/E for American Indian patients: 1.94 [95% CI: 1.30-2.78] versus O/E for White patients: 1.12 [95% CI: 1.10-1.14]), localized tumor stage (O/E for patients with localized disease stage: 1.13 [95% CI: 1.11-1.15] versus O/E for patients with distant disease stage: 1.04 [95% CI: 0.93-1.15]) and brain tumors (O/E for brain tumors: 2.54 [95% CI: 1.42-4.19]).Conclusion: Long-term cancer survivors (≥10 years) are more likely to die from Alzheimer's disease compared to the US general population. This risk seems to be higher among patients with older age at the time of cancer diagnosis, American Indian race and those with brain tumors.