RSNA: Your brain on chemo? PET/CT may enlighten its effects

CHICAGO—The role of 18F FDG-PET/CT has been validated as a diagnostic tool for chemo brain phenomenon, which may facilitate clinical diagnosis and treatment, based on a retrospective study presented Nov. 27 at the Radiological Society of North America (RSNA).

“This phenomenon is something that those of us who treat cancer patients have been struggling with because our patients describe a feeling of a ‘mental fog’ and not being able to make decisions after receiving chemotherapy,” said Rachel A. Lagos, DO, diagnostic radiology resident at the West Virginia University School of Medicine and West Virginia University Hospitals in Morgantown, W.Va.

Healthcare providers have generally referred to this occurrence as chemo brain for more than two decades. The specific symptoms associated with chemo brain include loss of memory, concentration, response time and daily organizational skills.

This study demonstrates PET/CT is diagnostic for this phenomenon, said Lagos, adding that “having diagnostic criteria will be one of the first steps in providing some relief to these patients.” She added that PET/CT “makes sense” as a diagnostic tool because it is accepted for other evaluations of cognitive decline, including Alzheimer’s disease and dementia.

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The researchers retrospectively reviewed 128 breast cancer patients’ staging and re-staging 18F FDG-PET/CT brain exams. These subjects did not have metastatic disease to the brain. In the study, they used NeuroMim neuroradiology analysis software to calculate the brain metabolism within 63 brain regions compared with a standard metabolism model for each diagnostic image set.

The researchers examined the PET/CT images pre- and post-chemotherapy. Z-score values measure is the “change or deviation from what the normal brain glucose metabolism should be in a person of that age,” said Lagos. Variance of these Z-score values was calculated for each patient prior to and post chemotherapy. The statistical significance of the changes in brain metabolism also was calculated within the total patient population. These results were clinically correlated with documented patient history, neurologic exams and chemotherapy regimens. Lagos et al also correlated the clinical presentation of chemo brain phenomenon and the statistically significant regional decreases in brain metabolism.

“In this population, it’s important that the person serves as her own control,” Lagos said. “We have seen across different age groups and individual patients, some individuals start out at a higher baseline than others, so making each patient her own control gives us a very strong assessment.”

The preliminary results of the study indicate that there are two brain regions that indicate statistically significant changes in glucose metabolism post chemotherapy, she reported. And these are some of the brain areas are responsible for problem solving, organizing daily activities and long-term memory, which correspond to the anecdotal evidence from patients.  

An example of one patient showed a baseline Z-score value of 2.247 in a pre-chemotherapy state, and a post-chemotherapy value of 0.481, which demonstrates a change of 1.766. The overall patient population underwent a Z-score value change range of 2.5 to 8.

One “surprising” finding was that the left-half of the brain was more impacted than the right-half of the brain in the majority of patients, which Lagos speculated could be attributed to the majority of patients being right-handed.

In women treated for breast cancer, the researchers reported that 18F FDG-PET/CT demonstrates statistically significant decreases in regional brain metabolism. The metabolic change correlates to chemotherapy regimen, neurological exam and symptoms of chemo brain phenomenon.

“The good news is that patients can cope with chemo brain, with a little help,” said Lagos, who recommended making lists of activities for these patients, so they can simply follow the list, as opposed to make it.

She and her colleagues hope that future studies will lead the way to better treatment for patients experiencing this condition. “The next step is to establish a prospective study that begins assessing new patients at the time of cancer diagnosis,” she said. “The prospective study has the potential to establish an understanding of the change in brain neurotransmitters during chemotherapy, which may lead to improved treatment or prevention.”