Many cancer survivors do not meet general recommendations for diet and exercise because of a multitude of common barriers, according to Erin Van Blarigan, ScD, Assistant Professor, Departments of Epidemiology & Biostatistics and Urology, University of California, San Francisco. These barriers can be linked to persistent treatment-related side effects, fatigue, conflicting advice, uncertain therapeutic benefit, or the desire to simply “move on” and resume normal life.
According to the 2012 American Cancer Society Nutrition and Physical Activity Guidelines for Cancer Survivors, survivors should engage in regular physical activity and exercise for at least 150 minutes weekly, including strength training twice a week. Diets should be rich in vegetables, fruits, and whole grains; limiting red and processed meats; and including whole overrefined grains.
“Emerging data do suggest that people who follow these guidelines have longer survival,” Dr Van Blarigan said at the 2018 Cancer Survivorship Symposium.
Physical Activity and Nutrition During and After Cancer
Research has consistently demonstrated that exercise during and after cancer treatment reduces symptoms and improves quality of life.
In a 2016 systematic review of 32 randomized, controlled clinical trials of more than 2600 women with breast cancer focused on exercise interventions during adjuvant therapy, the analysis showed that exercise improved physical fitness, cancer-related quality of life, cognitive function, muscle strength, fatigue, and mood disturbances.
An observational study of more than 500 women with colon cancer showed that those who increased their physical activity after diagnosis had a 50% lower risk for colon cancer–specific and all-cause death compared with patients who did not change their rate of physical activity. However, unlike the clear link between exercise and survival, the association between nutrition and survival in patients with cancer is more varied, according to Dr Van Blarigan.
For the purpose of analyzing dietary patterns in the United States, 2 main diets have been identified—the Prudent diet, which is rich in vegetables, fruits, legumes, fish, poultry, and whole grains, and the Western diet, which includes red meat, processed meat, high-fat dairy, refined grains, snacks, sweets, and desserts.
The LACE study of approximately 2000 women with early-stage breast cancer revealed that women who consistently followed the Prudent diet had a 43% lower mortality risk compared with those who did not follow the diet. In addition, a study of more than 1000 patients with stage III colon cancer showed that patients who had a diet consistent with the Western pattern had more than a 2-fold increased mortality risk compared with patients who did not follow the Western diet.
Many studies suggest that diet after a cancer diagnosis plays a bigger role in terms of cancer recurrence and survival, but separating the effects of individual foods and nutrients from overall dietary patterns or other lifestyle factors (eg, physical activity, weight) can be a challenge, Dr Van Blarigan said. Nonetheless, a healthy diet can help to reduce the risk for other causes of morbidity and mortality and potentially prevent cancer recurrence and progression.
To Supplement or Not to Supplement?
The American Cancer Society recommends that survivors should aim to meet their nutritional needs through a well-balanced diet, but dietary supplements can be used when deemed necessary.
“But it’s important to recognize that many dietary supplements contain levels that exceed amounts found in food or recommended for optimal health, so they should be used carefully,” Dr Van Blarigan advised.
The data on supplement use after a cancer diagnosis suggest the potential for benefit or harm, depending on whether the individual or population is deficient or sufficient in a particular nutrient.
“The story of vitamin D and colorectal cancer is a promising one,” Dr Van Blarigan told attendees. Results from the SUNSHINE trial revealed that patients with metastatic colorectal cancer who received high-dose vitamin D had longer progression-free survival than those using a standard vitamin D dose. However, in interpreting these results, Dr Van Blarigan said, it is important to note that vitamin D deficiency is decidedly common, especially in New England, where the study was conducted, she added.
However, dietary supplements have the potential for harm. Another study looked at antioxidant supplementation versus placebo during radiation therapy in patients with head and neck cancer. Among smokers, taking an antioxidant supplement during radiation therapy actually increased their risk for disease recurrence, cancer-specific mortality, and all-cause mortality by more than 2-fold, whereas the supplement showed no benefit or harm in nonsmokers.
“If needed, work with your doctor to determine if you actually need supplementation for an established deficiency or condition,” she advised.
The LIVESTRONG Foundation and the YMCA run 12-week, group-based exercise programs, offered at 20% of YMCA facilities throughout the country. These programs have been tested in a randomized controlled trial and have been shown to be effective at improving cardiovascular fitness and general quality of life and reducing cancer-related fatigue.
“There is hard evidence to show that participating in these programs can improve outcomes,” Dr Van Blarigan said.
Digital health interventions that use wearable physical activity trackers, such as the Fitbit, can also overcome barriers to physical activity by providing evidence-based tailored information, reminders and motivational messages, strategies and tips, and autonomy through self-monitoring.