For the new study, Noble and his colleagues exposed cell lines in a laboratory and in mice to doses of 5-FU, and then evaluated the drug's effects. The drug is used to treat malignancies of the breast, ovaries, stomach, colon and other sites.
The researchers found that 5-FU damaged specific kinds of cells in the central nervous system -- immature cells known as progenitor cells, which later differentiate into specialized cells.
Also damaged were cells called oligodendrocytes, which help produce myelin, the fatty substance that coats nerve cells and facilitates communication between cells.
"The damage at eight weeks was considerably greater than one day after treatment," Noble said. "Damage at six months was even greater than at six weeks."
The finding "means that there is a real physiological basis for the symptoms of 'chemobrain,'" said Dr. Christina A. Meyers, chief of the department of neuro-oncology at M.D. Anderson Cancer Center, in Houston, who wrote an accompanying comment. "Until we know enough to develop targeted treatments for it, there is still lots to do about it [and better to have it than the alternative]." Among the remedies are relaxation training to focus attention, exercise, cognitive rehabilitation and medicine such as anti-inflammatory agents, she said.
Another cancer expert praised the study.
"This is a very good animal model," said Dr. Patricia Ganz, director of cancer prevention and control at the University of California, Los Angeles Jonsson Cancer Center.
But she added a caveat: "This does not mean that everybody receiving this drug will have damage to their brain," she said. And, she added, this is the effect of just one chemotherapy drug, 5-FU. Today, 5FU is "rarely used in breast cancer treatment," she said.
Noble hopes to focus next on why the damage continues. Eventually, his research m
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