A new study adds to an emerging body of evidence suggesting that subtle physical changes in the brain may underlie the constellation of symptoms dubbed “chemobrain”—cognitive changes associated with cancer or cancer treatment that are most often experienced as difficulties with concentration, memory, multitasking, and planning.

Using an advanced imaging technique, European researchers found evidence that changes in cognitive functioning in women with breast cancer who were treated with chemotherapy are associated with physical alterations in the fibres that connect neurons in the brain. The study appeared in the Journal of Clinical Oncology.

The researchers used a type of magnetic resonance imaging (MRI) known as diffusion tensor MRI (DT-MRI) to detect changes in the brain’s white matter, which regulates communication among different brain regions. Previous studies have shown that damage to white matter can lead to changes in cognitive performance.   

Three groups of premenopausal women, whose median age was 43, participated in the study: 34 women with early-stage breast cancer who were scheduled to receive chemotherapy; 16 women with early-stage breast cancer who were not scheduled to receive chemotherapy; and 19 healthy, cancer-free control subjects.

Before receiving any chemotherapy, and again 3 to 5 months after completing their treatment, the chemotherapy-treated patients underwent whole-brain DT-MRI imaging and a series of neuropsychological and cognitive tests to measure abilities such as concentration, memory, and capacity to plan.

The patients who were not exposed to chemotherapy and the healthy control subjects underwent the same assessment at matched intervals. The three groups showed no difference in performance on the pretreatment tests.

In the follow-up tests, however, women in the chemotherapy-treated group performed worse on the neuropsychological tests and reported more cognitive problems than women in both control groups. This poorer performance correlated with findings on the DT-MRI imaging tests that indicated microscopic alterations to the white matter in the brains of the chemotherapy-treated women.

“These results suggest that microstructural [white matter] changes in patients exposed to chemotherapy may underlie their cognitive dysfunction,” wrote the study authors, who were led by Dr. Stefan Sunaert of University Hospital in Leuven, Belgium.

“Patient complaints of persistent cognitive difficulties after cancer treatment ends must not be dismissed,” wrote Dr. Patricia Ganz of the University of California, Los Angeles, in an accompanying editorial. But “fears of developing cognitive difficulties should not deter the use of potentially beneficial chemotherapy,” she cautioned.

Dr. Ganz added: “We can no longer deny the existence of this long-term effect of cancer treatment; we must work to tailor future treatments to minimize this adverse outcome.”

Source: NCI