"Two brain regions -- the superior medial frontal gyrus and the temporal operculum -- demonstrate statistically significant change in glucose metabolism postchemotherapy," said Dr. Rachel Lagos, a diagnostic radiology resident at West Virginia University School of Medicine, at a press briefing.
While prior studies have given clues, they've failed to definitively pinpoint the changes in the brain that cause the mental fog known as chemo brain -- a complaint among patients undergoing chemotherapy for cancer.
Lagos said the PET/CT imaging was precise. "When we looked at the results, we were surprised at how obvious the changes were," she explained. "Chemo brain phenomenon is more than a feeling. It is not depression. It is a change in brain function observable on PET/CT imaging."
Marked changes in z-scores were observed for areas of the brain known to affect mental agility, decision-making, problem-solving, sequencing, and long-term memory, Lagos said. Although the researchers did not calculate an average value for the change in z-scores of glucose metabolism pre- and postchemotherapy, values ranged from a decline of 2.5 to 8.0 points, she said.
"This corresponds to anecdotal evidence we're hearing from patients about how their life is being affected by chemotherapy," Lagos said. "The good news is that we are seeing evidence on PET/CT that is diagnostic for this phenomenon. Having diagnostic criteria is going to be one of our first steps to providing relief to people receiving chemotherapy."
She noted that "chemotherapy has long been associated with cognitive decline, including loss of memory, concentration, response time, and daily organization." The researchers decided to use PET/CT imaging because the technology had been used in Alzheimer's disease and other dementias as a diagnostic tool.
For their study, Lagos and colleagues evaluated imaging exams of 115 patients who had undergone chemotherapy for breast cancer. The patients had advanced disease, but none had metastases to the brain. They underwent scans prior to receiving chemotherapy and after the treatments were finished.
Dr. Max Wintermark, chief of neuroradiology for the University of Virginia, who moderated the press briefing, said that the results may be reassuring for women who experience chemo brain.
"Instead of those symptoms being dismissed, we can see there is a substrate for them," he said. "Just to know they are not inventing those symptoms, I think that will help them go through this difficult experience."
Lagos said that comparing scans conducted while women received chemotherapy to scans performed after treatment indicated that chemo brain tends to resolve once treatment is finished.