Study: Physical activity may prevent chemotherapy-related cognitive decline in women with breast cancer

IN-DEPTH REVIEW OF RESEARCH

Study background

Over 75 percent of breast cancer patients report cognitive problems during chemotherapy treatment that for some may persist for years. Previous research looked at how chemotherapy impacts cognition in patients with breast cancer compared with individuals without cancer. Findings showed that a patient’s cognitive function declined on tests that measured attention and visual memory from the beginning to the end of treatment compared to cancer-free people. Compared to cancer-free individuals, patients were also more likely to report cognitive complaints, such as troubles with recall and sustaining attention over time.

Physical activity greatly benefits individuals with chemotherapy-related cognitive decline. However, it remains unclear whether physical activity is important before or during chemotherapy.

Researchers of this study wanted to know

Researchers wanted to know if increased physical activity before, during or after chemotherapy improved cognitive function in patients.

Populations looked at in this study

This study included 580 women (average age of 53) who were receiving chemotherapy for early- to advanced-stage breast cancer (stages I to IIIC) and 363 cancer-free, age-matched women. Participants were recruited from 22 locations by the National Cancer Institution Community Oncology Research Program.

Study design

Participants filled out questionnaires about their physical activity and cognitive function at three intervals: seven days before chemotherapy treatment and within one month and six months after their last chemotherapy treatment. Cognitive function was also separately determined by scores on tests that measured attention span and visual recall.

Study findings

Among women who received chemotherapy for breast cancer, findings showed that:

• patients who engaged in moderate-to-vigorous physical activity throughout the study did not experience a meaningful decline in cognition. On the other hand, patients who never engaged in similar physical activity showed cognitive decline throughout the study.
   
  • prior to beginning chemotherapy, 33 percent of patients engaged in moderate-to-vigorous physical activity (e.g., household work, jogging, cycling, etc.) for at least 150 minutes per week.
  • at follow-up within one month of last treatment, fewer patients (21 percent) reported moderate-to-vigorous physical activity.
  • at the six-month follow-up after their last treatment, over 37 percent of patients reported engaging in moderate-to-vigorous physical activity patterns.
     
• patients who engaged in moderate-to-vigorous physical activity for at least 150 minutes per week before chemotherapy reported less cognitive complaints and a better attention span at the end of the study compared with those who were not as physically active.
• based on test scores, visual memory was better in patients who maintained high physical activity throughout the study, compared with those who were not as active. The highly active patients also had better cognitive recovery at the end of the study.
• patients who reported more exercise (with moderate-to-vigorous physical activity) at an assessment point had better cognitive function later. (For example, patients with high levels of physical activity at their one-month post-treatment follow-up had a better cognitive function at their six-month follow-up.)

When comparing patients with cancer-free women of similar age, study findings showed that:

• patients who had chemotherapy to treat breast cancer reported less time for moderate-to-vigorous physical activity prior to and during their treatment when compared with cancer-free women.
• the physical activity level of patients six months after they completed chemotherapy was similar to that of women who were cancer-free. 
  • Overall, the physical activity of cancer-free women was consistent throughout the study. The physical activity of patients decreased immediately after chemotherapy treatment but recovered to pre-chemotherapy levels by six months posttreatment.
• although moderate-to-vigorous physical activity was linked with similar cognitive outcomes for both cancer-free women and patients receiving chemotherapy, patients with cancer were more likely to report cognitive complaints.

Strengths and limitations

Strengths

• Because the study looked at physical activity during and after chemotherapy treatment, researchers could identify when it was most important for reducing cognitive decline.
• Women undergoing chemotherapy were compared to each other based on physical activity and to women of similar age without cancer.
• The study included both researcher-reported and patient-reported changes in cognition. This helped to provide multiple measures of cognitive decline in patients.
• The study included whether or not patients received anthracycline-based chemotherapy. This is important because anthracyclines have been linked to cognitive decline.

Limitations

• The physical activity of study participants was self-reported. Patients may not always recall or report activity accurately.
• No information was given on how long patients underwent chemotherapy. Patients may have undergone varying lengths and received varying doses of chemotherapy regimens, which could impact levels of physical activity and changes in cognitive function of patients during the study, especially since chemotherapy was shown to decrease both factors.
• Although the study contained information about the use of anthracycline chemotherapy, it did not provide information regarding whether anthracyclines caused cognitive decline in patients.
• No information was given about the type of breast cancer diagnosed or whether it was due to an inherited mutation. It is unknown whether there are differences in these groups of patients.
• The patient population was not racially or ethnically diverse (90 percent identified as white, 8 percent identified as Black, 3 percent identified as other races and ethnicities). No information was given about the impact of physical activity on cognitive decline among different races; only whole group information was given.

• Confounding factors  (other factors that may explain effects) may affect the interpretation of the findings. People who exercise less may have other features in common that differ from people who exercise more. Physical exercise is linked to less cognitive decline in people without cancer or chemotherapy treatment. How much of this effect is due to chemotherapy is unclear.

Context

Previous studies show that chemotherapy may induce cognitive decline in breast cancer patients. Engaging in moderate physical activity has been shown to increase the quality of life in people receiving chemotherapy.

This study adds additional data, showing that moderate-to-vigorous levels of physical activity before and during chemotherapy may reduce treatment-related cognitive decline.

Conclusions

This study showed that at least 150 minutes per week of moderate-to-vigorous physical activity (e.g., household work, jogging, cycling, etc.) may decrease the risk of chemotherapy-related cognitive decline in breast cancer patients. The authors suggest that physicians and health professionals should promote physical activity as an intervention to reduce chemotherapy-related side effects. Further research is needed to confirm the benefits and potential impact of physical activity before and during chemotherapy to minimize treatment-related cognitive decline.

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posted 1/6/22