Long after chemotherapy, nerve damage may increase a woman’s risk of falling

Years after completing treatment, nearly half of women cancer survivors continued to experience chemotherapy-induced peripheral neuropathy in a new study that tracked more than 500 survivors.

Those with neuropathy had worse physical functioning and a significantly higher risk of falls, the researchers reported this week at the American Society of Clinical Oncology Cancer Survivorship Symposium in San Francisco.

Peripheral neuropathy results from damage to the nerves that relay signals between the spinal cord and the rest of the body. It often causes numbness, tingling and pain in the hands and feet. The damage can also take away the sense of spatial positioning of arms and legs. “It’s often under-recognized and probably under-reported,” said oncologist Merry-Jennifer Markham, M.D., an associate professor of medicine at the University of Florida, who moderated a press event at the ASCO symposium.

“This study is important because it highlights that the neuropathy our patients are experiencing is not just a bothersome symptom,” Markham said. “Neuropathy from chemotherapy not only impacts our survivors’ physical function for years after treatment has ended, it also puts them at risk – much higher risk – for falls and the morbidity associated with those falls.”

Lead author Kerri Winters-Stone, Ph.D., a research professor at the OHSU School of Nursing and co-leader of the Knight Cancer Institute Cancer Prevention and Control Program, says the study is one of the first to examine the relationship between chemotherapy-induced neuropathy and physical functioning using both laboratory-based and patient-reported outcomes.

The researchers assessed baseline data from 512 women who had enrolled in clinical trials designed to test exercise interventions to prevent falls and fractures after cancer treatment. More than two-thirds of the women had breast cancer, and others had lung, colorectal, ovarian, or blood cancers.

Men may face similar risks

At an average of six years after cancer diagnosis, 45 percent of the women still reported having symptoms of peripheral neuropathy. Having symptoms was associated with significantly poorer physical functioning (measured by a series of clinical tests) and more self-reported difficulty doing activities of daily living, such as cooking and shopping.

The risk of falling among symptomatic women was nearly twice that of women without peripheral neuropathy symptoms. Men may face similar long-term risks. They are as likely as women to experience chemotherapy-induced neuropathy symptoms. Winters-Stone and colleagues only examined women cancer survivors because their clinical trials were based on data from larger studies, such as the Women’s Health Initiative, that first reported a higher risk of falls and fractures among women with cancer.

Altered walking patterns – not muscle weakness – appeared to be the underlying factor among the women in the new study. Leg strength (measured by maximal leg press) did not differ between women with neuropathy and those without. That finding has implications for how to best target rehabilitation exercise programs.

Rehabilitation implications

Machine-based resistance training, for example, may not be the right type of exercise program because lack of strength doesn’t appear to be the major problem, Winters-Stone says, and because these exercises are done in a non-weight bearing position that doesn’t translate well to how we move in daily life. Rehabilitation efforts, she says, should focus on specific gait training and improving balance during upright movement. Because of the increased risk of falling due to altered gait, she says walking for exercise may be more safely done on a treadmill with handrails rather than outdoors.

Winters-Stone and her research team are developing a portable, smartphone-driven device that patients can use to detect and quantify symptoms of neuropathy, such as gait and balance impairments. The goal is to detect symptoms as early as possible and potentially take actions to minimize disabling symptoms, for example, by adjusting chemotherapy dosing or starting rehabilitation interventions early.

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The study was supported by grants from the National Cancer Institute, American Cancer Society, and Susan G. Komen Breast Cancer Foundation. ASCO has posted the research abstract online.