Chemotherapy causes changes in the brain's
metabolism and blood flow that can last as
long as 10 years, a discovery that may explain
the mental fog and confusion that affect many
cancer survivors, researchers said.
The researchers, from
the University of California, Los Angeles,
found that women who had undergone chemotherapy
five to 10 years earlier had lower metabolism
in a key region of the frontal cortex.
Women treated with chemotherapy also showed
a spike in blood flow to the frontal cortex
and cerebellum while performing memory tests,
indicating a rapid jump in activity level,
the researchers said in a statement about
their study.
"The same area of the frontal lobe that showed
lower resting metabolism displayed a substantial
leap in activity when the patients were performing
the memory exercise," said Daniel Silverman,
the UCLA associate professor who led the study.
"In effect, these women's brains were working
harder than the control subjects' to recall
the same information," he said in a statement.
Experts estimate at least 25 percent of chemotherapy
patients are affected by symptoms of confusion,
so-called chemo brain, and a recent study
by the University of Minnesota reported an
82 percent rate, the statement said.
"People with 'chemo brain' often can't focus,
remember things or multitask the way they
did before chemotherapy," Silverman said.
"Our study demonstrates for the first time
that patients suffering from these cognitive
symptoms have specific alterations in brain
metabolism."
The study, published on Thursday in the online
edition of Breast Cancer Research and Treatment,
tested 21 women who had surgery to remove
breast tumors, 16 of whom had received chemotherapy
and five who had not.
The researchers used positron emission tomography
scans to compare the brain function of the
women. They also compared the scans with those
of 13 women who had not had breast cancer
or chemotherapy.
Positron emission tomography creates an image
of sections of the body using a special camera
that follows the progress of an injected radioactive
tracer.
Researchers used the scans to examine the
women's resting brain metabolism as well as
the blood flow to their brains as they did
a short-term memory exercise.
Silverman said the findings suggested PET
scans could be used to monitor the effects
of chemotherapy on brain metabolism. Since
the scans already are used to monitor patients
for tumor response to therapy, the additional
tests would be easy to add, he said.
Breast cancer is the most common cancer among
women, with some 211,000 new cases diagnosed
each year, the statement said.
