For many patients who have received chemotherapy for breast cancer, cancer-related fatigue is a persistent side effect—and one that contributes to ongoing balance problems, suggests a recent paper published by Weschler et al in Rehabilitation Oncology.

The new research by Stephen Wechsler, PT, DPT, PhD, of the MGH Institute of Health Professions, and colleagues is the first to quantify and compare the relative contribution of cancer-related fatigue to postural instability to that of chemotherapy-induced peripheral neuropathy. "Our results... indicate that cancer-related fatigue, even several years following exposure to chemotherapy, may distinctly influence balance independent of a patient's chemotherapy-induced peripheral neuropathy status," the researchers wrote.

Cancer-Related Fatigue Predicts Greater Postural Sway and Changes in Sit-to-Stand Function

Following breast cancer treatment, many patients experience physical or functional limitations, including balance problems and an increased risk of falls. These balance problems are often attributed to peripheral neuropathy—nerve damage that frequently occurs as an adverse effect of chemotherapy. However, recent studies have suggested that cancer-related fatigue, another common side effect of cancer and its treatment, may also contribute to balance problems.

To examine the relationship between cancer-related fatigue and postural instability, Dr. Wechsler and colleagues analyzed data on 43 women who had undergone chemotherapy for breast cancer. Patients were studied for an average of 3.5 years after cancer treatment. Consistent with the high reported frequency of cancer-related fatigue, average score for fatigue was 43 on a 0 to 100 scale, with higher scores indicating greater fatigue. More than half of the women (53.5%) had at least mild chemotherapy-induced peripheral neuropathy symptoms.

Participants underwent a series of standardized assessments of balance function. In a static (standing still) balance test, women with higher cancer-related fatigue scores had increased anteroposterior (front-to-back) postural sway. After adjustment for other factors, cancer-related fatigue score accounted for about 10% of the variation in postural sway, compared to the 1% accounted for by chemotherapy-induced peripheral neuropathy.

Women with more severe cancer-related fatigue also had increased postural sway after a brief exercise task. In both tests, postural sway was not significantly related to the severity of chemotherapy-induced peripheral neuropathy.

Further tests evaluated the effects of cancer-related fatigue on dynamic balance during a standard sit-to-stand test, a key measure of physical functioning and a predictor of the risk of falling. In this test, after a fatiguing exercise targeting the muscles of the lower extremities, cancer-related fatigue accounted for nearly 7% of the variance in postural sway compared to the 3% accounted for by chemotherapy-induced peripheral neuropathy.

After exercise, participants with greater cancer-related fatigue showed "smaller, more conservative" forward shifts in body weight during the sit-to-stand test. That pattern is consistent with a "stabilization strategy" commonly seen in individuals with balance problems. Dr. Wechsler and colleagues noted that the stabilization strategy is suggestive of impaired postural control as it relies more on lower leg strength, compared to the "momentum transfer" strategy observed in people with better balance function.

Implications of Cancer-Related Fatigue

The researchers discuss several clinical implications of their findings—most notably, that a lower-extremity-fatiguing task may cause or exacerbate impairments in dynamic balance among survivors with cancer-related fatigue. Survivors may encounter such fatiguing tasks in everyday life through performing activities of daily living, negotiating stairs or the community, or participating in a recommended exercise program.

The report adds to recent studies suggesting that cancer-related fatigue after chemotherapy and other treatments may contribute to balance problems and risk of falls in breast cancer survivors. "While chemotherapy-induced peripheral neuropathy remains a risk factor for imbalance in this population, cancer-related fatigue warrants consideration in clinical practice and research as a mechanism of postural instability," Dr. Wechsler and coauthors concluded.

The findings may have implications for rehabilitation professionals making exercise prescriptions for cancer survivors, particularly in terms of improving dynamic balance to reduce the risk of falls. In particular, patients with cancer-related fatigue after cancer treatment "may benefit from balance-related education regarding safety and coping or compensatory strategies," the researchers added.

Disclosure: For full disclosures of the study authors, visit journals.lww.com/rehabonc.