Exercise for Cancer Survivors Facing Bone Loss
Osteoporosis literally means porous bones, from the Greek. Approximately 40 million people in the United States currently have osteoporosis or low bone mass, and more than three quarters of them are women.
There is now a growing awareness that women who are breast cancer survivors face an even greater risk of developing osteoporosis, compared to their cancer-free counterparts. Hormone therapies such as aromatase inhibitors (AIs) can reduce estrogen levels, which can accelerate bone loss. Chemotherapy may induce early menopause, which again, reduces estrogen levels and that hastens bone loss. The cancer itself and/or other treatments may also cause some small amount of bone loss.
“For healthy women, bone loss in the first five years after menopause can be as much as 2 to 5 percent,” says Tish K. Knobf, PhD, RN, Professor at Yale University, who presented at the AICR 2013 Annual Research Conference. “For women with cancer who go through chemotherapy-induced menopause, they may lose between 5 and 10 percent of their bone mass a year. Survivors treated with aromatase inhibitors for five years can lose an additional 2 to 4 percent per year and are known to be at increased risk for fractures.
“We know non-pharmacologic interventions like exercise, vitamin D and calcium help to preserve bone mass in healthy postmenopausal women…. Women completing cancer therapy should be getting the same prescription for health promotion,” says Knobf.
Low bone mass occurs when the cells that break down bone – the osteoclasts – outpace the cells that form new bone, the osteoblasts. During peri-menopause and in the years following menopause, women naturally lose bone at a higher rate than they form it. When bone mass dips too low, the condition is recognized as osteoporosis and the weakened bones can lead to falls and fractures, a major barrier to normal functioning and being active.
The goal with exercise – and other interventions – is to maintain bone mass, not lose it. The exercise needs to put weight or a load on the bones to stimulate osteoblast growth. Examples include wearing or lifting weights, squats, jumps and other exercises that work against gravity.
In a paper on exercise and cancer for the Annual Review of Nursing Research, Knobf and her colleague found eight exercise trials among women cancer survivors that investigated bone health. Most of the women were breast cancer survivors. Trial participants varied in ages, type of exercise, duration and timing of treatment. Overall, the trials suggest that exercise maintained bone mass or minimized bone loss compared to usual care or control groups, said Knobf.
Benefits of exercise in cancer patients are relatively small, but these changes could have large long-term effects for preventing fractures and falls.
Modifiable risk factors for osteoporosis include:
- vitamin D and calcium (diet)
- imiting alcohol
- not smoking
Balance, Falls and Training
“We know bone loss is a problem for breast cancer survivors, and now we’re seeing they fall more, too,” says Kerri Winters-Stone, PhD, a Research Professor at Oregon Health & Science University, who co-authored the paper with Knobf. “What we’re trying to understand now is what might be underlying these falls and prevention strategies.”
Trials by Winters-Stone and her colleagues have shown that moderate-intensity resistance plus impact exercises may prevent or minimize bone loss and improve muscle strength among postmenopausal breast cancer survivors.
She has found success in a bone-loading training program, including resistance that works muscles that attach to the spine or hip. After months of strength training, Winters-Stones adds an impact component to the program: jumping.
“This is based on a huge number of research studies outside of cancer, pointing to the benefits of impact loading,” said Winters-Stone, who comes from an exercise physiology background. The researchers were evaluating what led some athletes to have high bone densities and they pinpointed it to the impact portions of their training. “The impact delivers force to the bone, and that force hits the skeleton, it doesn’t break – if it keeps getting repeated, the bone gets stronger,” she says.
For exercise, “breast cancer survivors should be following the current guidelines for women at risk for osteoporosis,” said Knobf. That’s aerobic exercise most days of the week and resistance exercises three days a week.
Excerpted from AICR's ScienceNow.