The treatment of colorectal cancer (CRC) with chemotherapy was found to be associated with a reduced risk of developing Alzheimer disease (AD) and dementia, according to the results of a retrospective study published in JCO Oncology Practice.

“Although additional validation is required, such findings may be used to reduce the potential treatment-related anxiety among patients with cancer worried about the potential adverse effects of guidance-concordant care,” the authors wrote.

The retrospective study included a cohort of 135,834 patients aged 65 and older from the SEER-Medicare database who were diagnosed with CRC between 1998 and 2007. Medicare claims data were used to identify cases of AD or other neurocognitive disorders (ND) and previous treatment with chemotherapy. Pseudo-randomization was used to address selection bias.

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Within the cohort, the overall rate of AD was 7.22%, AD-related dementias (ADRD) was 18.4%, ADRD without AD was 17.4%, dementia as a permanent mental disorder was 13.02%, dementia/senile was 9.35%, vascular dementia was 3.28%, and cerebral degeneration without AD was 11.27%.

Chemotherapy was associated with a lower risk of AD (hazard ratio [HR], 0.791; 95% CI, 0.758-0.824), ADRD (HR, 0.823; 95% CI, 0.802-0.844), dementia as a permanent mental disorder (HR, 0.807; 95% CI, 0.782-0.832), and dementia/senile (HR, 0.772; 95% CI, 0.745-0.801).

The association was found to be time dependent, with the protective effect decreasing over time. Within 7 to 9 years after a diagnosis of CRC, the protective effect of chemotherapy was no longer significant.

In contrast with AD and dementia, the investigators noted an increased risk of cerebral degeneration with chemotherapy (HR, 1.067; 95% CI, 1.033-1.102).

The authors concluded that “the results of our study support the hypothesis that receipt of chemotherapy in CRC survivors is associated with reduced risk for AD after adjusting for patient-, cancer-, and treatment-related characteristics.”


Akushevich I, Yashkin AP, Kravchenko J, Kertai MD. Chemotherapy and the risk of Alzheimer’s disease in colorectal cancer survivors: evidence from the Medicare system. JCO Oncol Pract. Published online February 25, 2021. doi:10.1200/OP.20.00729