Research has documented that cancer patients can exhibit cognitive deficits that persist even at 5 years after treatment. However, how long these cognitive deficits last or whether they worsen and become more apparent in older age--when the risk for cognitive dysfunction is higher--is not known.
To determine the extent of cognitive deficits in cancer patients, Beth E. Meyerowitz, Ph.D., of the University of Southern California in Los Angeles, and colleagues conducted a study of 702 cancer survivors from Sweden and their cancer-free twins using data collected through the Karolinska Institute.
All cancer survivors and those who had survived cancer for 5 or more years were twice as likely as their cancer-free twins to have cognitive dysfunction. (Cognitive function was assessed using a structured telephone interview.) Cancer survivors were also twice as likely to be diagnosed with dementia, but this result was not statistically significant. The authors conclude that cancer patients have an increased risk for long-term cognitive dysfunction compared with individuals who have never had cancer.
"Our data suggest that cancer and its treatments may lower survivors' cognitive reserve and thus increase their long-term risk of cognitive dysfunction and dementia, a serious clinical concern for physicians treating cancer survivors," the authors write. "Further research should identify mechanisms that mediate the relationship between cancer and cognitive dysfunction and explore whether specific treatments are associated with long-term cognitive effects. This knowledge will help health care providers and patients make informed decisions about treatments."
In an editorial, Jeffrey S. Wefel, Ph.D., and Christina A. Meyers, Ph.D., of the University of Texas M. D. Anderson Cancer Center in Houston, urge caution when interpreting the results the this study. "Recent studies have demonstrated that cognitive dysfunction may be present before treatment, may worsen acutely secondary to treatment-related neurotoxicity, and may continue after cessation of therapy," they write. They call for more studies to determine which treatment regimens are the most neurotoxic, how and which cognitive and behavioral domains are most affected, and the risk factors for this neurotoxicity.
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JNCI Journal of the National Cancer Institute