Alzheimer’s disease showed different connections with various types of cancers and, even, both are protecting from each other. Some studies attributed it to shared genetic backgrounds. One of the shared mutations is located on APOE4 gene, a risk factor in Alzheimer’s, and was connected to chemotherapy-related deterioration of cognitive functions in breast cancer patients. Our aim is to examine the addon effect of radiation therapy on the risk of death from Alzheimer’s disease.
We collected data from 13 USA cancer registries enrolled in Surveillance Epidemiology and End Results program using SEER*stat software. We enrolled patients diagnosed with head and neck cancers or brain cancers between 1992 and 2016. The event was defined as death due to Alzheimer’s disease following the cancer diagnosis. Moreover, we have calculated Multiple Primary Standardized Incidence Ratios and excess risk per 10,000 person-years, to estimate the change of risk following the diagnosis when compared to the general population. Besides, we calculated the effect of gender, age, and receiving radiation for cancer.
Out of 142,541 patients (59,630 patients with brain malignancies, and 82,911 with head and neck malignancies), 151 died due to Alzheimer’s after more than 10 years following a cancer diagnosis; 20 had brain malignancies, and 131 had other head and neck malignancies. The risk of Alzheimer’s death increased significantly after more than 10 years of a cancer diagnosis with an O/E ratio of 1.35 and an excess risk of 2.72 per 10,000. The risk increased significantly among females (81 females and O/E was 1.4) and males (70 and O/E was 1.29). Alzheimer’s was the cause of death in 52 patients who received Radiation therapy, and 13 patients who received chemotherapy with O/Es of 1.45 and 1.59 respectively. The risk of disease-related mortality was high in patients older than 70 years, while patients who were diagnosed with cancer earlier did not show a significant increase in their risk of Alzheimer’s death than the general population.
Risk of Alzehimer’s-related mortality increases significantly among survivors of head and neck cancers and brain cancers. Further studies shall address the biological risk-modifying effects of aging, gender, and treatment.
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All authors have declared no conflicts of interest.