For breast cancer patients battling "chemo brain," regular exercise may be a powerful prescription, a new study suggests.

The term "chemo brain" refers to thinking and memory problems often experienced by patients who undergo chemotherapy.

It's "a growing clinical concern," said study first author Elizabeth Salerno, an assistant professor of surgery at Washington University School of Medicine in St. Louis. "Some patients with cancer experience memory lapses, difficulty concentrating or trouble finding the right word to finish a sentence."

In the study, Salerno's team analyzed data from 580 U.S. breast cancer patients and a control group of 363 without cancer.

Before chemo, 33% of the cancer patients met government guidelines calling for at least 150 minutes of moderate to vigorous physical activity per week.

During chemo, that fell to 21%, then rose to 37% six months after treatment. Rates in the control group were about 40% at all three time points.

Researchers also assessed four types of mental skills. Cancer patients who got the recommended levels of exercise before and after chemo outperformed those who never met the guidelines.

Those in the control group had similar results on the mental assessments, regardless of their exercise habits.

Significantly, results of memory and attention tests among breast cancer patients who met the activity guidelines before chemo were similar to those of people in the control group.

However, the active cancer patients still perceived a significant decline in thinking skills, especially during chemo, according to findings published online Aug. 18 in the Journal of Clinical Oncology.

The findings lay the groundwork for future clinical trials on whether moderate to vigorous exercise can ward off chemo brain, the authors said.

"Our findings suggest that maintaining higher levels of physical activity may indeed be important for protecting cognition in patients with breast cancer undergoing chemotherapy," Salerno said in a university news release.