Cancer risk increases as people age. According to the American Cancer Society (ACS), two of every three invasive breast cancers are diagnosed in women age 55 and older, so it is important for postmenopausal women to maintain a healthy lifestyle as they get older. 1
A study published in Cancer Epidemiology, Biomarkers and Prevention reviewed data from the ACS Cancer Prevention Study II Nutrition Cohort of 73,615 postmenopausal women. Of that group, 4,760 women were diagnosed with breast cancer between 1992 and 2009.
For this specific patient population, the study revealed that there is a way to offset the risk of breast cancer—by exercising daily. Postmenopausal women who walked for 7 hours each week were able to lower their risk of breast cancer by 14%. Those who exercised vigorously (ie, running, swimming or playing tennis) for 1 hour each day showed a 25% lower risk of breast cancer.2
Extended Cox regression was used to estimate relative risk (RR) of breast cancer in relation to total recreational physical activity, walking, and sitting. The data shows that the association between physical activity and postmenopausal breast cancer does not differ by estrogen receptor status, body mass index (BMI), weight gain, or postmenopausal hormone use. Larger prospective studies of these attributes may shed light on how these characteristics impact breast cancer prevention or diagnosis.
Alpa Patel, MD, Senior Epidemiologist at the ACS, listed compelling reasons for why medical professionals should encourage regular exercise in their patients. “Given that more than 60% of women report some daily walking, promoting walking as a healthy leisure-time activity could be an effective strategy for increasing physical activity among postmenopausal women,” he said in a press release.
It is important to note that not all women who exercised were free from cancer diagnoses; it is just one piece of the prevention strategy puzzle. It is crucial to look at other factors, including genetics, diet, and stress, to assess risk and to create prevention strategies for patients.
Benefits of Moderate Activity
Physical exercise was also noteworthy in a meta-analysis of 76 studies that found high levels of exercise were associated with lower breast cancer incidence (RR, 0.80; 95% CI: 0.78-0.84).3 The meta-analysis, published in the journal Breast, showed that moderate activity (ie, 3 to 4 hours of walking per week) may reduce breast cancer incidence, and benefit women with early-stage breast cancer by lowering their risk of recurrence. Other factors, such as diet and use of vitamin supplements, were studied; however, the influence of dietary intake was difficult to separate from the influence of body weight and requires further study to fully interpret how they affect cancer risk or risk of recurrence.
Obesity’s Connection to Breast Cancer Risk
Walking may help keep patients’ weight stable, which is important because obesity increases the risk of breast cancer and is also associated with poor prognosis in both pre- and postmenopausal women.4 According to a study from the University of Austin in Texas, this connection between obesity (defined by having a BMI greater than 30)5 and breast cancer results from specific factors that can influence breast tumor initiation and progression, and/or response to therapy.4
“These host factors include components of the secretome, including insulin, insulin-like growth factor-1, leptin, adiponectin, steroid hormones, cytokines, vascular regulators, and inflammation-related molecules, as well as the cellular and structural components of the tumor microenvironment,” the abstract states. The researchers suggest that these factors should be considered potential targets in breast cancer prevention.
What should medical professionals tell their patients? Get moving. Keep moving. Every day.
1. Risk factors for breast cancer. American Cancer Society. http://www.cancer.org/cancer/breastcancer/detailedguide/breast-cancer-risk-factors. Last accessed October 11, 2013.
2. Hildebrand JS, Gapstur SM, Campbell PT, et al. Recreational physical activity and leisure-time sitting in relation to postmenopausal breast cancer risk. Cancer Epidemiol Biomarkers Prev. 2013 Oct;22(10):1906-1912.
3. Chlebowski RT. Nutrition and physical activity influence on breast cancer incidence and outcome. Breast. 2013 Aug 1;22S2:S30-S37.
4. Ford NA, Devlin KL, Lashinger LM, et al. Deconvoluting the obesity and breast cancer link: Secretome, Soil and Seed Interactions. J Mammary Gland Biol Neoplasia. 2013 Oct 4. [Epub ahead of print]
5. Defining overweight and obesity. Centers for Disease Control and Prevention. http://www.cdc.gov/obesity/adult/defining.html. Last accessed October 11, 2013.