Joining FORCES is the FORCE newsletter with news, views and supportive information for individuals concerned about hereditary breast and ovarian cancer.
by Tracy M. Diaz, PhD
Several studies have linked obesity to poor breast cancer outcomes. Among women with early-stage breast cancer, some research has found that obese women have an increased breast cancer mortality risk as high as 33% compared to non-obese women. Other studies link exercise with increased survival. One project demonstrated that weight loss using a low-fat diet after diagnosis could reduce risk of recurrence. While these studies show a connection between weight and breast cancer risk, none have involved women who purposefully lost weight as part of their breast cancer treatment. A recent editorial written by Dr. Jennifer Ligibel, a professor of medicine at Harvard Medical School, examines the connection between obesity and breast cancer, and summarizes the implications of the Reach Out to Enhance Wellness (RENEW) and Nutrition and Exercise for Women (NEW) studies, projects that looked into the potential effects of weight loss for breast cancer risk.
The RENEW study tested the efficacy of telephone-based intervention to implement long-lasting changes in diet, physical activity, and weight in 641 survivors of colon, prostate, and breast cancers. Eligibility included having a sedentary life style and a cancer diagnosis at least five years before enrollment. Participants were assigned to a one-year lifestyle intervention performed over the phone, supplemented by print materials that were designed to increase physical activity and improve dietary quality. Subjects were randomized to begin immediately or to delay receiving the materials for one year. Researchers looked for change in physical functionality. The results showed that favorable changes in physical activity, dietary behaviors, and weight were maintained in the immediate intervention group for up to one year after finishing the program.
The NEW trial evaluated the impact of different lifestyle interventions on hormones that are linked to breast cancer risk and prognosis. This study randomly assigned 439 postmenopausal, sedentary, and overweight women to groups with different regimens. The first regimen consisted of dietary weight loss, while the second focused on exercise alone. A third group practiced dietary weight loss with exercise. The control group did not change their diet or exercise habits. Researchers looked for changes in hormones including estrogen, testosterone, and insulin that have been linked to breast cancer risk. Women assigned to the weight loss groups saw favorable changes in hormones compared to the controls. Patients assigned to the exercise regimen saw smaller but still significant changes in some, but not all of the same hormones as the diet group. This observation is consistent with the beneficial effects of weight loss for breast cancer patients. One important note is that this study was performed in postmenopausal women at risk for breast cancer, and did not include cancer survivors.
The RENEW study demonstrates how implementing a safe and inexpensive program can have a positive impact on cancer survivors, while the NEW study shows that weight loss, especially through dietary changes, can reduce hormones that are associated with breast cancer risk in postmenopausal women.
Tracy Diaz received her Ph.D. in Cancer Biology from the UT Southwestern Medical Center in Dallas. She is currently employed as a medical writer and volunteers her expertise and time to FORCE. She is a BRCA2 mutation carrier.
Ligibel JA and Goodwin PJ. NEW and RENEW: Building the case for weight loss in breast cancer. Journal of Clinical Oncology vol. 30 no. 19 (2012): 2294-96.
Denmark-Wahnefried W, Morey MC, Sloane R, et al. 'Reach Out to Enhance Wellness homebased diet-exercise intervention promotes reproducible and sustainable long-term improvements in health behaviors, body weight, and physical functioning in older, overweight/obese cancer survivors.' Journal of Clinical Oncology vol. 30, no. 19 (2012): 2354-61.
Campbell KL, Foster-Schubert KE, Alfano CM, et al. Reduced calorie dietary weight loss, exercise, and sex hormones in postmenopausal women: Randomized controlled trial. Journal of Clinical Oncology vol. 30, no. 19 (2012): 2314-26.