The study, published early in the online edition of the journal Cancer, comes from Japan.
The scientists noted several differences in the scans of women who had gotten chemotherapy in the previous year. Those women had less volume in certain brain areas tied to memory and attention.
However, brain scans taken three years after the chemotherapy showed no differences among breast cancer patients who had gotten chemotherapy, those who hadn't gotten chemotherapy, and the healthy women.
The results suggest chemotherapy may have a "temporary effect" on brain structure, the researchers write.
The researchers included Masatoshi Inagaki, MD, PhD, of the National Cancer Center Hospital East in Chiba, Japan.
The women were in their mid-to-late 40s, on average.
The scans were taken with magnetic resonance imaging (MRI) and were part of a Japanese cancer database.
It's not clear whether chemotherapy caused the brain changes or whether the women had noticed any changes in their memory or attention.
"These findings can provide new insights for future research to improve the quality of life of cancer patients who get chemotherapy," write Inagaki and colleagues.