Imaging chemotherapy’s effects on the brain
Caren B. Les
Breast cancer survivors who have endured mental fogginess and forgetfulness
following chemotherapy can take some comfort in the fact that “chemo brain”
has been validated as a condition.
A study using functional neuroimaging has shown
that chemotherapy affects the brain’s metabolism and blood flow, causing changes
that can last at least 10 years following treatment. Because the majority of women
diagnosed with breast cancer now achieve long-term survival, the lingering side-effects
of treatment are an important consideration. Chemo-brain symptoms, which include
confusion, disrupted thought processes, and difficulty focusing or multitasking,
are experienced by at least 25 to 82 percent of survivors, according to estimates.
Daniel H.S. Silverman and his colleagues
at the University of California’s David Geffen Medical Center in Los Angeles
used positron emission tomography (PET) and cognitive testing to investigate their
subjects. They scanned the brains of 21 women who had undergone breast cancer surgery
five to 10 years earlier, 16 of whom had been treated with chemotherapy near the
time of their surgeries.
These fluorodeoxyglucose PET images represent a horizontal slice through the brains of three women at rest,
one of whom had breast cancer and received chemotherapy (far left). The other two
images are from women who received no chemotherapy, one who had the disease (middle)
and one who did not (right). The color reflects the metabolic activity of the brain
cells — with the red, orange and yellow areas (in decreasing order) representing
the most active regions and the green, blue and violet areas progressively showing
the less active areas. The ages of the women were, from left to right, 55, 55 and
51. Courtesy of Daniel H.S. Silverman.
They compared the images with brain
scans of five breast cancer patients who had surgery only and with those of 13 control
subjects who had neither the disease nor the treatment. As the women performed short-term
memory exercises, the team measured blood flow to their brains. They also ran scans
of the women’s resting brain metabolism after the women finished the exercises.
The scans revealed a link between chemo-brain
symptoms and lower metabolism in a key region of the frontal cortex. They showed
that blood flow to the frontal cortex and cerebellum spiked as the chemotherapy
patients performed the tests.
This rapid jump in activity in these
areas indicated that these women’s brains were working harder than the control
subjects’ to recall information. The researchers also found that women who
received hormonal therapy in addition to chemotherapy showed changes in the basal
ganglia, a part of the brain that bridges thought to action.
Additional studies are needed to determine
how the alterations in the brain occur and the possible ways in which to prevent
them, including modification of chemotherapy drugs. A long-term study of chemo-brain
symptoms in a larger group of cancer survivors is planned.
Breast Cancer Research and Treatment, online, Sept. 29, 2006.
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