People with Alzheimer disease may be less likely to develop cancer, and people with cancer may have a lower risk of AD, according to a large population-based epidemiological study published online this week in Neurology. The work, from Catherine Roe and colleagues at Washington University in St. Louis, Missouri, puts legs under the idea that the molecular pathways underlying cancer and neurodegeneration could be related—a concept that that has been percolating through the field for some time.
The new study follows up on previous work from the same researchers (Roe et al., 2005) that suggested an inverse relationship between the two diseases. This time, Roe and colleagues looked at the question in a group of 3,020 people age 65 or older who had enrolled in a long-term cardiovascular health study. The investigators asked whether time to a first hospitalization for cancer was related to the prevalence of dementia, and conversely, whether the chances of dementia were changed in people with a history of cancer. The subjects were followed for an average of 5.4 years for dementia and 8.3 for cancer.
The results showed that people with a diagnosis of AD at baseline had a 60 percent reduced risk of cancer compared to subjects without AD. The association was specific for AD, as it was not seen with vascular dementia. Likewise, people with a history of cancer had a 30 percent lower risk of developing AD during follow-up.
In an accompanying editorial, David Bennett and Sue Leurgans of Rush University in Chicago point out some caveats, the most important of which is the possible effect of mortality on the observed associations. Nonetheless, they write, the uncovered associations are worthy of further exploration.
Paul Coleman of the University of Rochester, New York, wrote in an e-mail to ARF that he agrees with the cautions of Bennett and Leurgans, adding that he has previously looked at comorbidity of AD and cancer using an extensive database at the Marshfield clinic in Wisconsin. That dataset is a remarkable one, he wrote, with extensive records on a relatively stable cohort of tens of thousands of people. “In a nutshell, these data showed no relationship between the two (once age was factored out). But I was unsatisfied with the ascertainment of the cancer cases (all lumped together) so this result has never been published,” Coleman wrote.
Roe’s results, pending replication, would support the idea that there may be a common molecular mechanism linking cancer and AD. Independent studies have unearthed evidence for a similar link between neurodegeneration and cancer in Parkinson disease (Driver et al., 2007; Inzelberg et al., 2007). The common thread could be pathways implicated in cell death and survival, or epigenetic regulation (see ARF related news story on Mastroeni et al., 2009). Alternatively, perhaps chemotherapy has an unexpected upside for neurons—a recent study suggests that women who had chemotherapy for breast cancer were at a reduced risk of AD (Du et al., 2009). Whatever the reason, the concept of AD and cancer as opposite sides of the coin of age-related diseases could lead researchers to new insights into neurodegeneration. This coming April, the Ipsen Foundation will hold a conference entitled: Two Faces of Evil: Cancer and Neurodegeneration in Paris, France.—Pat McCaffrey
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