“Cognitive complaints of people increase with chemotherapy and we
are trying to find out why,” said Sabine Deprez, who led the new
study. “Difficulty multitasking is one of the biggest complaints.”
Past research has documented changes in mental performance following
chemotherapy – and in some cases, in cancer patients before
chemotherapy, suggesting disease-related processes may also play a
role, according to Deprez’s team.
Other studies have used imaging to show differences in brain
activity between cancer patients who had chemotherapy and healthy
people not being treated for cancer, the researchers write in the
Journal of Clinical Oncology.
To compare women with themselves before and after chemo, as well as
with other women, Deprez and her colleagues at the University
Hospital Gasthuisberg of the Katholieke Universiteit Leuven, used
functional Magnetic Resonance Imaging (fMRI).
The imaging technique indirectly assesses brain activity by
signaling changes in blood and oxygen delivered to various regions
of the brain.
Eighteen women with breast cancer scheduled to receive chemotherapy
performed a multitasking exercise in an MRI machine before starting
treatment and four to six months after treatment ended.
Two comparison groups - one of women with breast cancer not
scheduled to receive chemotherapy and another of healthy women -
also performed the tasks.
“The special thing about how we did the design was that before we
did it we adjusted the difficulty for each patient, and the
performance of everyone was between 70 and 80 percent,” Deprez said.
That meant patients’ performance on the test, which included
indicating if two sounds were the same frequency and if two moving
circles with lines through them were at the same orientation or not,
while remembering two symbols presented earlier, did not change over
time. This allowed the researchers to measure changes in brain
activity levels during the task, not in the women’s ability to
complete the task, Deprez said.
Neither of the two comparison groups seemed to change in terms of
the parts of the brain activated by the tasks or their level of
activation, while in the chemotherapy group brain activation
significantly decreased, the authors report.
Meanwhile, patients in the chemotherapy group also complained of
“foggy thinking” more than those in the other groups. Before the
chemotherapy started, all the participants had about the same amount
of cognitive complaints.
“The important thing that we found was a relation with subjective
cognitive complaint,” Deprez told Reuters Health.
[to top of second column]
The decreased brain activation seen with fMRI may help explain why
many chemotherapy patients complain of chemo brain.
“It feels like they have to do more effort to get the same result
after chemo,” Deprez said.
That could be because chemotherapy causes structural changes in the
brain, but experts still don’t know, she said.
Functional MRI is very useful for research, but for the cognitive
effects of cancer treatment it can only be used to draw conclusions
about people in general, not individual patients, Brenna C. McDonald
told Reuters Health in an email.
McDonald, of the Radiology and Imaging Sciences department at
Indiana University School of Medicine in Indianapolis, has
investigated this topic but was not part of the new study.
“There is a more limited literature suggesting that other cancer
treatments, like antiestrogen therapies, may be related to some
cognitive symptoms, but this effect, if present, appears to be
smaller than the effects noted after chemotherapy,” McDonald said.
“Generally, however, the most significant effects have been shown
with regard to chemotherapy.”
Patients who are older at diagnosis seem to be at greater risk for
foggy thinking problems from chemotherapy, she added.
“As we advance our understanding of which patients are at greatest
risk, hopefully we will be able to personalize medical treatment to
minimize cognitive risks while still effectively treating the
cancer,” McDonald said.
“Being aware of the possibility of cognitive effects of treatment is
important in the same way it is important to know about other
possible treatment-related side effects,” she said.
Journal of Clinical Oncology, online May 27, 2014.
[© 2014 Thomson Reuters. All rights
Copyright 2014 Reuters. All rights reserved. This material may not be published,
broadcast, rewritten or redistributed.