化療後腦力會比較鈍，稱為 "Chemo Brain"，可用fMRI證實

乳癌患者接受化療後，常會訴腦筋鈍了，認知能力降低，但因為沒有科學研究依據，常常被以為是 "心理作用"，被稱為 "Chemo Brain"。現在有利用functional MRI的研究顯示這些病人的腦部功能的確有損傷。

年老(age)以及原有的認知能力 (congnitive reserve)對一個人的認知能力影響最大。盡量使用腦力可以增強cognitive reserve。

'Chemo Brain': MRI Shows Brain Changes
After Chemotherapy

Fran Lowry

November 16, 2011 — Breast cancer survivors who have been
treated with chemotherapy show significant changes in brain activity,
measured by functional magnetic resonance imaging (fMRI), according to a
study published in the November issue of the Archives of
Neurology.

The finding validates patients' claims of reduced
cognitive function after receiving chemotherapy, a phenomenon referred to as
"chemo brain," said lead author Shelli R. Kesler, PhD, from
Stanford University School of Medicine in California.

"Emerging research shows that there is a biological
correlate of these cognitive problems that these patients are reporting,"
Dr. Kesler told Medscape Medical News. "Historically, there has
been some controversy as to whether these problems really exist, so looking at
the brain and seeing that there are brain changes validates patients'
experiences."

She added that she hopes these findings will be helpful for
breast cancer survivors who are experiencing such problems, "so that they
are less likely to be turned away for things like disability benefits or even
to be ignored by their physicians, who sometimes tell them that they're just
imagining the problem. Our study shows that there really is a problem. It's not
just stress. It's not their imagination. It's a real brain change."

Performing Card-Sorting Task

In this observational study, Dr. Kesler and her team sought
to ascertain differences in prefrontal executive function between 25 breast
cancer survivors who underwent chemotherapy, 19 women who did not, and 18
healthy women with no history of breast cancer. All subjects were matched
for age and other demographic variables.

All women underwent fMRI while performing a card-sorting
task that was designed to measure prefrontal brain activation associated with
executive function and while performing a control task in which they were
asked to judge whether a single card was red.

All 3 groups showed a similar profile of brain activation
during the fMRI tasks, including bilateral cerebellum, basal ganglia, and
parietal and dorsolateral prefrontal regions.

However, the results showed that the women with breast cancer
demonstrated significantly reduced activation of the left middle dorsolateral
prefrontal cortex and premotor cortex, compared with the healthy women.

In addition, breast cancer survivors who received
chemotherapy showed significantly reduced left caudal lateral prefrontal cortex
activation, increased perseverative errors, and reduced processing speed,
compared with the other 2 groups.

The researchers also found that this reduced activation
in the left caudal lateral prefrontal cortex was significantly correlated with
higher disease severity and self-reported executive dysfunction in the
chemotherapy group.

Groundbreaking Study

Michelle C. Janelsins, PhD, from the James P. Wilmot Cancer
Center, University of Rochester School of Medicine and Dentistry, in New York,
told Medscape Medical News that she thinks this study is
"groundbreaking, excellent, and extremely interesting."

"What is most interesting about this study is that Dr.
Kesler and colleagues were looking at specific areas of the brain and trying to
associate these areas with specific types of processes, such as problem
solving, decision making, and planning," Dr. Janelsins said.

"We are always looking for indicators of subclinical
problems that might predict longer-term impairment so that we can manage them
if it looks as if the person is developing cognitive deficits," she said.
"Not every single individual develops cognitive deficits; brain imaging
may be a way to allow us to determine who is most at risk and who is most
affected by chemotherapy for breast cancer."

"Chemo Brain" Not All in
the Mind

Dr. Kesler said that older women and those who were less
physically and mentally active were more likely to be cognitively affected by
chemotherapy.

"Two of the things we found that predicted more
cognitive dysfunction were age and cognitive reserve, so the older you are, the
more vulnerable, which is not surprising since you are more vulnerable to a lot
of things," she said.

"When you have been more mentally and physically
active, [cognitive reserve] tends to give you more brain capacity, so when
something like breast cancer and chemotherapy happens to you, you have more
capacity to overcome that," she said.

Dr. Kesler hopes this research will lay the foundation for
future longitudinal studies that will evaluate patients before and after
chemotherapy. "These are going to be critical for figuring out this
problem. It's hard to get funding to do those studies unless you have evidence
such as that from our study, showing that cognitive dysfunction is a real
problem."

This study was supported by the National Institutes of
Health. Dr. Kesler and Dr. Janelsins have disclosed no relevant financial
relationships.

Arch Neurol.
2011;68:1447-1453. Abstract

Medscape Medical News
© 2011 WebMD, LLC

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