Specific Cancer Types Linked to Dementia Subtypes and Impact of Chemotherapy 

A recent study published in Alzheimer’s & Dementia reveals significant bidirectional links between specific cancer types and dementia subtypes. 

To better understand this complex relationship, researchers conducted a comprehensive search of databases, including Embase, Medline, and American Psychological Association PsycInfo, focusing on studies published between 1980 and 2024. The analysis included 42 studies, encompassing more than 3.8 million individuals. The primary objectives were to examine the association between specific cancer types, such as chemotherapy and endocrine therapies, and dementia risk, while the secondary objective was to explore the risk of cancer among patients with dementia.

The researchers found that cancer survivors had an 8% to 14% lower risk of developing all-cause dementia (ACD), Alzheimer’s disease (AD), and vascular dementia (VaD) compared to those without cancer. 

In contrast, individuals with ACD, AD, and VaD demonstrated a roughly 25% lower risk of developing cancer. These inverse associations were particularly notable for colorectal cancer, which was associated with a 16% reduced risk of ACD, a 13% reduced risk of AD, and a 24% reduced risk of VaD. Similarly, lung cancer was linked to a 17% reduction in AD risk, while melanoma reduced VaD risk by 27%. AD patients also had a 20% lower chance of developing breast cancer while ACD patients had a 26% lower risk. 

The study revealed both protective and adverse effects of various treatments. Tamoxifen was associated with a 21% reduction in the risk of AD, while chemotherapy showed an 18% risk reduction. In contrast, prostate cancer patients undergoing androgen deprivation therapy faced a 26% increased risk of ACD and a 9% higher risk of developing AD.

Subgroup analyses revealed that the protective effect of cancer against dementia was more evident in studies that accounted for apolipoprotein E genotype or distinguished between existing and newly diagnosed cancer cases. While patients with lung cancer or non-melanoma skin cancer exhibited a significantly reduced risk of developing dementia.

“[T]he current study deepens our understanding of the intricate relationship between cancer and dementia. It underscores a reciprocal association, indicating varying impacts on risk between these conditions,” the researchers concluded. 

Study limitations include differences in study designs, reliance on observational data leading to potential bias, and inconsistencies in diagnostic criteria and treatments across studies.

This research was supported by the National Health and Medical Research Council (Australia), Alzheimer’s Association USA, Dementia Australia Research Foundation, and NHMRC-AMED collaborative dementia research.

This article originally appeared on Psychiatry Advisor