PET/CT Pinpoints Physiological Evidence Of Chemo Brain

PET/CT scans routinely used in the care of oncology patients may prove useful in pinpointing physiological changes associated with chemo brain.

An analysis of 18F-fluorodeoxyglucose (18F-FDG) PET/CT images taken before and after chemotherapy in breast cancer patients revealed significant declines in glucose metabolism in two key regions of the brain. The affected areas were the superior medial frontal gyrus and temporal operculum, which are responsible for mental agility, problem solving, daily decision making, sequencing, and long-term memory, Dr. Rachel Lagos reported at the annual meeting of the Radiological Society of North America.

Dr. Rachel Lagos

Interestingly, no changes in metabolism were observed in 61 other regions of the brain studied.

“If we can come up with an answer to explain why that is, or to reverse this, then we can solve the problem,” Dr. Lagos said in an interview. “The good news is that we already know what these two areas do, so we know at a social level what to prepare women and their families for. We can give them some tools for coping, rather than just a pat on the hand.”

Although many cancer patients complain of a mental fog or loss of coping skills, some clinicians remain skeptical without definitive scientific evidence. Previous studies have used magnetic resonance imaging, but this modality only allows clinicians to see anatomic details such as small losses in brain volume. With PET/CT, one can see the effects of chemotherapy on brain function over time, explained Dr. Lagos, a diagnostic radiology resident at West Virginia University in Morgantown.

The retrospective analysis involved PET/CT scans taken at the time of initial cancer staging and 12 months after chemotherapy from 116 women with advanced breast cancer, all of whom also received tamoxifen (Nolvadex, Soltamox). The investigators compared the scans to identify areas of reduced 18F-FDG uptake, representing lower glucose metabolism, and then plotted the changes as Z-score values. One patient with brain metastases was excluded from the analysis.

Statistically significant declines in glucose metabolism were observed post chemotherapy in the superior medial frontal gyrus as a whole (P = .025), when it was evaluated from left to right (P = .023), and in the temporal operculum (P = .036), Dr. Lagos said.

The investigators did not calculate an average value for the change in Z scores, but the decline in values ranged from 2.5 to 8.0 points, she said.

In 21 patients, the affected regions of the brain regained their metabolism, which corresponds to anecdotal information from patients that chemo brain lifts about 1-2 years after treatment.

Dr. Patrick Peller

“With the small data I’ve been able to accumulate so far, it’s hopeful that this kind of brain phenomenon is temporary,” Dr. Lagos said.

The next step is to prospectively assess brain function starting at the time of cancer diagnosis and continuing throughout long-term follow-up, which potentially could lead to improved treatments or prevention, she said. In the meantime, the results provide physiologic evidence for chemo brain, and may prompt peers and counselors to use simple interventions such as creating lists for patients of their daily activities or meal plans to compensate for the mental fog.

Dr. Patrick J. Peller, a radiologist with the Mayo Clinic in Rochester, Minn., who hosted the poster session, said the study provides an understanding of the substrate for the often frustrating symptoms that patients experience, and could facilitate interventions to prevent chemo brain.

“Once you have a way to measure something, it sometimes drives your ability to treat it,” he said in an interview. “We don’t have that treatment right now, just like we don’t have treatment for Alzheimer’s disease, but my sense is that it’s possible that our treatment for Alzheimer’s might work in some of these patients because it helps in compensation and not actually changing the underlying disease.

“If it improves the patient’s memory function, it might work in this situation, and you might be able to measure if it’s working with this technique.”

Dr. Lagos and Dr. Peller reported no relevant financial disclosures.

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