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She had
been, she says, “a
smart cookie,” a university grad who had built up a successful
business in Toronto as a marketing consultant. But
several years ago, when she was 38, she had chemotherapy for breast
cancer and wound up with a bad case of “chemo brain” ---
cognitive problems such as trouble with thinking and memory that
many cancer patients, and a growing number of doctors, believe may
be related to chemotherapy. Starting
with her third round of chemotherapy, says this woman, who asked not
to be identified, “I lost my sharpness. Memory became a huge
issue. It was like being drunk without being drunk.” Since she
had never heard of “chemo brain,” she adds, she was terrified. After
years of being dismissed as a figment of patients’ imaginations or
as a result of anxiety or depression, “chemo brain” is beginning
to be taken seriously by cancer doctors and researchers. Indeed,
it appears to be fairly common, affecting as many as 16 to 40
percent of women undergoing chemotherapy for breast cancer, says Dr.
Ian Tannock, the Daniel E. Bergsagel professor of medical
oncology at Princess Margaret Hospital and professor of medicine and
medical biophysics at the University of Toronto. So far,
most studies of “chemo brain” have been in women with breast
cancer, but “chemo brain” can affect both men and women. In one
study by Tannock and others, women who had undergone chemotherapy
for breast cancer fared worse, as a group, on certain cognitive
tests than a similar group of women without cancer. The differences
in cognitive functioning could not be explained by differences
in age, education, menopausal status or mood. Luckily,
says Tannock, the
problem is usually mild to moderate: “These women are not
demented. It’s a subtle thing.”
The problems usually improve after chemotherapy but in some
cases may persist for years. At the
Netherlands Cancer Institute, researchers have conducted a number of
studies suggesting that chemotherapy is linked to cognitive
deficits. In one study
published in 1998, they found cognitive impairment in 32 percent of
women with breast cancer given high dose chemotherapy and in 17
percent of patients getting standard dose chemotherapy. On
average, the women were studied two years after treatment. Another
Dutch study in 1999 also found that breast cancer patients who got
chemotherapy had significantly more cognitive impairment than those
who did not. At
Dartmouth-Hitchcock Medical School, psychologist Tim Ahles and his
team studied 71 men and women who had had chemotherapy for breast
cancer or lymphoma and 57 similar people who had received only
surgery and localized radiation for those cancers. Five years after
treatment, all were cancer-free, but those treated with chemotherapy
fared worse on paper-and-pencil cognitive tests than those who did
not get chemotherapy. Still,
“chemo brain” is tough to explain. At least until recently,
it’s been thought that most drugs used in chemotherapy do not
cross the blood-brain barrier, the protective membrane that acts a
filter between substances in the circulating blood and the brain.
(One notable exception is methotrexate when given in very high
doses.) Indeed,
many chemotherapy drugs are too big or have chemical properties that
prevent them from crossing the blood-brain barrier, says Dr.
Lawrence Shulman, chief medical officer at Boston’s Dana-Farber
Cancer Institute. In fact, this is a major reason why most
chemotherapy drugs are ineffective at treating cancers that have
spread to the brain. But
“chemo brain” could be caused by chemotherapy drugs indirectly.
Even though most chemotherapy drugs do not cross the blood brain
barrier, they can cause the body to pump out natural chemicals
called cytokines that do enter the brain and may trigger significant
decreases in cognitive function. Cancer
cells themselves also pump out cytokines, notes Christina Meyers, a
professor of neuropsychology at the M.D. Anderson Cancer Center in
Houston, TX. That might explain why some cases of “chemo brain” seem to set in even before treatment starts, she says. And some
cognitive problems experienced by cancer patients might be caused by
drugs given along with chemotherapy, like anti-nausea medications,
steroids, sedatives and antihistamines. Rachel
Morello-Frosch, 37, an assistant professor of environmental studies
at Brown University who had chemotherapy for breast cancer 10 years
ago while she was in graduate school, never could figure out what
caused her “chemo brain.” Yet for three or four days after every
treatment, she would “have a conversation with someone and
completely forget what they said.” she says. Part
of the problem understanding “chemo brain” is that definitive,
longterm tests – on the same patients before, during and after
chemotherapy – have not been done, says Cheri Geckler, a
neuropsychologist at Tufts-New England Medical Center. Another
part is that it’s proven hard to tease apart, at least in women
with breast cancer, whether “chemo brain” comes from
chemotherapy per se or from the fact that chemotherapy plunges some
women into abrupt menopause, which can cause hormonal,
mood and sleep disturbances that can affect cognitive
performance.. And
“none of these studies has been done in large enough numbers or
with good enough controls for us to be certain of what’s going
on,” cautions Dr.
John Glaspy, an oncologist at the Jonsson Comprehensive Cancer
Center at the University of California, Los Angeles. Potential
treatments for “chemo brain” are at an even earlier stage.
Researchers are considering drugs used to treat Alzheimer’s,
stimulants, drugs used to treat anemia and the related fatigue that
can lead to some cognitive impairment.. As for
the Toronto marketing consultant, memorization exercises, and the
sheer passage of time since chemotherapy, have helped. “My
brain is different,” she says. She now has to use notes to deliver
presentations that she wrote herself and used to know by heart.
“My brain is about 90 percent back. But the rest has not come
back.
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