Cancer survivors are more likely to suffer difficulties with mental tasks than people without cancer, according to the June 1 issue of the Journal of the National Cancer Institute.
Researchers at the University of Southern California studied Swedish twins aged 65 and older. They compared mental tasks in each pair. One twin had been diagnosed with cancer and the other had not.
The researchers write that previous studies have shown that cancer survivors often experience a decline in mental tasks, but it remains "unknown how long these deficits last or whether they worsen over time.
"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.
In the study, 700 cancer survivors and their twins were compared in tests of mental skills such as memory, verbal recall, and general knowledge.
Overall, 15 percent of the cancer survivors had difficulties compared with 9 percent of the cancer-free twins. Cancer patients were also more likely to have dementia.
The researchers note higher rates of difficulties even in those individuals who had survived cancer five or more years before the study began. They suggest future research "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."
Editorial Criticizes Study's Conclusions
An editorial by neuro-oncologists at the University of Texas M. D. Anderson Cancer Center questions the study's conclusion. The authors say it is premature to suggest reduced mental reserve is the cause of thinking difficulties in cancer patients. They say it's possible that "persistent neurotoxicity" of cancer treatments may be to blame instead and future studies should investigate which treatment regimens are most toxic to the brain and nerve cells.
The editorial expresses particular concern about the suggestion that cancer patients tend to suffer long-term thinking impairment. "The conclusion that cancer patients are at risk for developing new late-onset cognitive dysfunction and dementia ... was not supported and could potentially alarm patients and providers."
SOURCES: Heflin, L. Journal of the National Cancer Institute, June 1, 2005; vol 97: pp 854-856. Wefel, J. Journal of the National Cancer Institute, June 1, 2005; vol 97: pp 788-789.