BETHESDA, MD—Research is mounting that exercise can help cancer survivors, especially breast cancer survivors, stay healthy and avoid bone loss and fractures, according to speakers here at the annual research conference of the American Institute for Cancer Research (AICR). The organization's latest Cancer Risk Awareness Survey Report, though, shows that Americans' overall awareness of insufficient physical activity as a cancer risk factor actually dropped by 10 points—from 46 percent in 2009 to 36 percent in 2013.
The awareness level on physical activity had risen from 2005 to 2009, before taking the precipitous drop in 2013. Calling the finding “alarming,” AICR commented that because Americans are becoming more obese and less active, “this is precisely the worst possible time for awareness of this key cancer-protective strategy to be on the wane.”
Breast cancer survivors in particular are at risk of bone loss due to chemotherapy, early menopause, and adjuvant treatment with aromatase inhibitors (AIs), which block bone-stimulating estrogen.
Tish Knobf, PhD, RN, FAAN, AOCN, Professor at Yale School of Nursing and a member of the Yale Cancer Center Research Center reported that data from the 12-month Yale Fitness Intervention Trial (Yale FIT) showed that exercise may minimize the rates of bone loss due to anti-estrogen adjuvant therapy after breast cancer. Nine published exercise intervention studies with breast cancer survivors “suggest preservation of bone with exercise compared with bone loss in controls,” she said. Still, she added, the variability of study designs and the different exercise prescriptions have made it difficult to draw definitive conclusions.
Knobf studied 154 women with an average age of 52, of whom 132 had bone outcomes that could be evaluated. Of these women, 30 percent were on AIs, 31 percent were on tamoxifen, and 39 percent had no endocrine therapy. About half the study subjects in the Yale FIT study went to a fitness center three times a week for an aerobic/resistance exercise program, while the other half was given standard national recommendations for 30 minutes of moderate-intensity physical activity on most days of the week. Both groups were given guidelines on healthy nutrition and calcium as well as vitamin D supplementation.
The study found that aerobic resistance exercise at the fitness center markedly increased bone turnover and markers of bone formation for women on AI therapy and no endocrine therapy, while women on tamoxifen—regardless of the type of exercise—had no significant change.
The women in the aerobic fitness-center group also showed improved signs of cardiovascular health and metabolic health, increased physical endurance, increased muscle mass, and decreased fat mass.
“Both aerobic and resistance exercise have important health benefits for breast cancer survivors and many of these survivors are interested in non-pharmacologic health interventions,” said Knobf.
“Many breast cancer survivors are medication-averse. They really don't want a pharmacological intervention unless it's absolutely necessary.” But, she noted, while they are being treated and after treatment, “not every provider tells these women they are at increased risk of bone loss, and this is the time survivors need to be aware . . . If you can prevent or minimize how much bone is lost with exercise, that would be powerful.”
Also speaking at the conference, Kathleen Y. Wolin, ScD, FACSM, Associate Professor of Public Health Sciences and Surgery at Stritch School of Medicine at Loyola University, said that many survivors of breast cancer are not receiving DEXA scans for bone loss on a regular basis, and there is no consensus on how often they should be done.
She added that patients with gynecological cancers tend not to be screened for osteoporosis. “Bone remodeling involves many of the biologic factors known to be responsive to exercise such as cytokines, and while many survivors, particularly those of breast cancer, are prescribed bisphosphonates as part of clinical care, medication adherence may be inconsistent.”
She noted that although a recent systematic review of trials on the effect of exercise on bone concluded that the studies were too limited and too few to draw major conclusions, “the results were encouraging for the benefits of physical activity on bone health in cancer patients.”
In recognition of the importance of physical activity and cancer, the University of Texas MD Anderson Cancer Center recently established the Center for Energy Balance in Cancer Prevention and Survivorship. “The increasing toll of Americans' largely sedentary lifestyle and its links to cancer is just beginning to be understood,” said the new center's Director and Professor of Behavioral Science at MD Anderson, Karen Basen-Engquist, PhD, MPH—who spoke at a session on social media and cancer research.
“But we have evidence that going from being completely sedentary to just a little bit active is where we'll see the most benefit in cancer survivors and, probably, in the general population as well. This is important because it's a ‘do-able’ thing for most people.”
Awareness of Cancer Risk Factors, 2013
In addition to showing that Americans' awareness of physical inactivity as a cancer risk factor dropped by 10 points from 2009 to 2013, the AICR survey report showed that:
1. Awareness of all six established lifestyle-related cancer risk factors dropped. They are: obesity; insufficient physical activity; diets low in vegetables and fruits; drinking alcohol; diets high in red meat; and eating cured meats preserved by salt, nitrates, nitrites or sugar.
2. Prior to the 2013 AICR survey, the public's awareness of these six lifestyle risk factors had been trending upward. But today, more than half of respondents failed to correctly identify any of these six as cancer risk factors.
3. Particularly troubling given the high U.S. obesity rates is that only 48 percent of respondents correctly identified being overweight or obese as a cancer risk factor. Today, seven out of 10 Americans are overweight or obese, and excess body fat causes an estimated 117,000 U.S. cases of cancer annually, according to statistics from AICR.
4. An overwhelming majority of Americans did correctly identify tobacco use (92%) and excessive sun exposure (84%) as cancer risk factors.