People with chemo brain often report loss of mental sharpness, including increased lapses in concentration, difficulty remembering certain things, and problems finishing tasks.
The study - led by Michelle C. Janelsins, an assistant professor of surgery in the Wilmot Cancer Institute at the University of Rochester Medical Center in New York - is published in the Journal of Clinical Oncology.
Researchers have various terms for chemo brain, such as cancer treatment-related cognitive impairment, cancer-therapy associated cognitive change, and post-chemotherapy cognitive impairment.
Typically, people with chemo brain report increased lapses in concentration, difficulty remembering certain things, problems finishing tasks, or difficulty learning new skills.
Usually, the mental changes that patients notice are very subtle - and the people around them may not even notice them. Many patients do not mention these changes to their cancer care team until they start to affect everyday life.
The team behind the new research notes that while we know that chemo brain can be an important problem for patients, limitations in previous studies have left many questions unanswered. In particular, we do not know when and why chemo brain arises, and who is most at risk.
Pervasive issue for as long as 6 months after treatment
For their study, Prof. Janelsins and colleagues compared self-reported problems with memory and thinking among 581 female breast cancer patients and 364 matched healthy women (the controls). The patients were from several clinical centers across the United States, and the average age of both groups was 53 years.
The self-reported data came from a well-validated questionnaire called the Functional Assessment of Cancer Therapy-Cognitive Function (FACT-Cog) that the participants filled in. This probes a person's own view of any cognitive impairment, as well as how others perceive it.
The researchers were particularly interested in how long the problems lasted and whether they were linked to factors that could influence them, such as age, education, race, and menopausal status.
Their analysis found that 45.2 percent of the breast cancer patients reported a perceived decline in FACT-Cog scores between before and after chemotherapy. This compared with 10.4 percent of controls reporting a perceived decline over the same period.
From the end of chemotherapy to 6 months later, 18.4 percent of breast cancer patients reported "clinically meaningful perceived decline" in FACT-Cog scores compared with 11.5 percent of controls.
The researchers suggest a significant finding was that from prechemotherapy to 6-months follow-up - a period spanning approximately 1 year - 36.5 percent of patients with breast cancer reported a decline in FACT-Cog scores compared with 13.6 percent of controls.
They also found that experiencing more symptoms of anxiety and depression prechemotherapy had a greater effect on the scores. Being younger and of a black race also appeared to influence cognitive decline.
The results also showed that patients who underwent hormone therapy or radiation treatment following chemotherapy had similar cognitive problems to women who only received chemotherapy.
"Our study, from one of the largest nationwide studies to date, shows that cancer-related cognitive problems are a substantial and pervasive issue for many women with breast cancer."
Prof. Michelle C. Janelsins
The team is now looking more closely at their results alongside other data to try and understand any biological link between cancer treatment and cognitive changes in patients.