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From our good fried Dr. Susan Love's website.
Warmest Regards
Joe
Low-Fat Diet and Exercise May Reduce Risk of a Breast Cancer Recurrence
June 9, 2005
What can I do to keep my cancer from recurring?
It’s a question common to all women who have had breast cancer. Now, two new studies-one that looked at diet and another that looked at exercise-appear to suggest that lifestyle changes may help keep a cancer recurrence at bay. Can they? Should you put down that doughnut and head to the gym?
The findings about the benefit of a low-fat diet come from the Women’s Intervention Nutrition Study (WINS), which was designed to test whether a low-fat diet could help reduce a breast cancer recurrence in postmenopausal women with early stage breast cancer. The findings were presented in May at the 2005 American Society for Clinical Oncology annual meeting.
The WINS study randomized 2,437 postmenopausal women who had completed their breast cancer treatment to one of two groups. Forty percent (975) of the women received eight individual counseling sessions that taught them how to reduce fat in their diet by cutting back on butter and other oils, eating more fruits, vegetables, fish, poultry, and egg whites, and substituting lower-fat foods for higher-fat ones. The other 60 percent (1,462 women) received no counseling and were expected to stay on their standard diet.
The researchers followed the women for 60 months (5 years). The women who were taught how to reduce the amount of fat in their diet had an average daily fat intake of 33.3 grams. Those who stayed on their regular diet had an average daily fat intake of 51.3 grams. After five years, 9.8 percent (96) of the women on the low fat diet had experienced a recurrence compared with 12.4 percent (181) of those on their regular diet.
The effect of a low-fat diet was most noticeable among the 478 women with estrogen receptor (ER)-negative tumors. Within this group, 13.7 percent (28) of the 205 women on the low-fat diet had a recurrence compared with 21.6 percent (59) of the 273 women who were on their regular diet.
There were 1,959 women with ER-positive tumors in the study. Within this group, 8.8 percent (68) of the 770 women on the low-fat diet had a recurrence compared with 10.3 percent (122) of the 1,189 women on their regular diet. The difference between these groups was very small, and not statistically significant (which means it could have happened by chance).
Based on their findings, the researchers concluded, "Life-style intervention resulting in dietary fat intake reduction may improve the relapse-free survival of postmenopausal breast cancer patients."
The study that found that exercise appeared to reduce the risk of a breast cancer recurrence was published in May in the Journal of the American Medical Association.
This study evaluated the relationship between exercise and breast cancer among 2,987 women taking part in the Nurse’s Health Study who were diagnosed with stage I, II, or III breast cancer between 1994 and 1998. The women were followed until 2002.
The women were asked to assess how much time they spent each week taking part in activities such as walking, hiking, running, bicycling, swimming, tennis, and aerobics. Each activity was assigned what researchers refer to as a metabolic equivalent task (MET) score. One MET is the energy expended when sitting quietly. Walking at an average pace is a 3, jogging is a 7, and running is a 12.
There were 463 deaths during the time the women were followed, 280 of which were due to breast cancer. The study found that the women with higher MET-hours per week were less likely to die of breast cancer: 110 of the women who died took part in less than 3 MET-hours per week whereas 42 took part in 24 or more MET-hours per week.
There were also 370 breast cancer recurrences. The study found that those women who had higher MET-hours per week were less likely to have a breast cancer recurrence: 137 of the women who had a recurrence took part in less than 3 MET-hours per week whereas 51 took part in 24 or more MET-hours per week.
Among women who engaged in at least 3 MET-hours per week, 97 percent were alive after five years. In contrast, 93 percent of the women who took part in less than 3 MET-hours per week were alive after five years. After 10 years, 92 percent of the women who took part 9 or more MET-hours per week were alive, compared with 89 percent of those who took part in 3 to 8.9 hrs., and 86 percent of those who took part in less than 3 MET-hours per week. The benefit was the same for both normal weight women and overweight women.
The study found that the type of exercise did not matter. Both walking and vigorous exercise, like aerobics, contributed to lowering the risk of dying from breast cancer or having a cancer recurrence. In fact, women who engaged in as little as the physical equivalent of walking one hour per week were less likely to die of breast cancer than were women who exercised less than that or not at all. Whether women exercised before their diagnosis or began exercising after their diagnosis also did not appear to make a difference. The maximum benefit occurred among women who performed the equivalent of walking 3 to 5 hours per week at an average pace (2-2.9mph).
The effect of exercise was most noticeable among women with hormone receptor-positive (ER- or PR-positive) tumors. Six percent (38) of the 609 women with hormone receptor-positive tumors who took part in 9 or more MET-hours per week died, whereas 9 percent (13) of the 149 women with hormone receptor-negative tumors who took part in 9 or more MET-hours died.
Based on their findings, the researchers concluded, "Women with breast cancer who follow the Center for Disease Control and Prevention recommendations to exercise at moderate intensity for 30 or more minutes per day for five or more days per week may survive longer."
Susan says:
I worry that women will read about these studies and think: If only I’d exercised more or not eaten so much high-fat foods, my cancer wouldn’t have recurred. But take a good look at both studies. There were women in each of them who did the “right” thing-be it eating a low-fat diet or exercising-who had their cancer recur. And there were women who did not exercise and who did not change their diet who did not have their cancer recur.
Cancer is very complicated. We don’t yet know how to keep all women from having a breast cancer recurrence. That’s why it is important to find out whether there are things that a woman can do, be it a treatment, like chemotherapy, or a lifestyle change, like diet or exercise, that can help reduce the risk of having breast cancer recur.
Many researchers are studying diet and exercise and breast cancer. But ascertaining whether there is a link between these lifestyle factors and a cancer recurrence has been difficult. Diet and exercise studies can be hard to design and carry out. And even once the data is in, it can be difficult to assess the findings. Is it really a low-fat diet or exercise that is significant? Or is it weight loss or other factors related to a low-fat diet or exercise that are the true reasons why cancer does not recur?
Let’s look at the study on the low-fat diet and breast cancer recurrence first.
The researchers followed 2,437 postmenopausal women who had been diagnosed with early-stage breast cancer for five years. Forty percent of the women were taught how to reduce the fat in their diet. Sixty percent were left on their own.
Interestingly, a low-fat diet appeared to have more of a benefit in women with ER-negative tumors: 13.7 percent of those on the low-fat diet has a recurrence, compared with 21.6 percent of the women who did not change their diet, an absolute difference of 7.9 percent. For women with ER-positive tumors, the effect of dietary change was so small it was not statistically significant (which means it could have happened by chance.)
Why this would be the case isn’t clear. The researchers theorized that reducing fat in the diet might have decreased the amount of insulin in the blood (insulin levels have been linked to tumor growth) thereby reducing the risk of recurrence. It’s also possible that the women who changed their diets began to eat more fruits and vegetables, which had a protective effect. Or it may be that the women on the low-fat diet began to exercise more or lost weight.
Previous studies have suggested that women who lose weight after a breast cancer diagnosis are less likely to have a recurrence. Researchers have theorized that losing weight reduces the amount of circulating estrogens that fuel ER-positive breast cancer, thereby reducing the risk of recurrence. Yet in this study, the women who benefited most from a low-fat diet were those with ER-negative tumors, which are not fueled by estrogen- a surprising and unexpected finding.
Should you eat a low-fat diet? In general, diets that are lower in fat are lower in cholesterol, which can help reduce your chance of having a heart attack or heart disease. This is significant because more women who have had breast cancer die from heart disease than they do from breast cancer. Also, a low-fat diet can help people lose weight, and people who are overweight are at higher risk for many health problems.
Bottom-line: Eating a low-fat diet may help you reduce your risk of recurrence if your tumor is ER-negative, but whether it is beneficial to women with ER-positive tumors is less clear. Eating a low-fat diet can’t hurt you, and it may help you lose weight. In addition, it may help you avoid other health-related problems, especially heart disease.
Now, let’s look at the exercise study.
Previous studies have found that women who exercise are at lower risk of getting breast cancer. This study found that women who exercise-even those who walk as little as one hour per week-were less likely to die of breast cancer than those women who exercised less than that or not at all. However, this only appeared to be true for women with ER-positive tumors. Women with ER-negative tumors did not have the same benefit.
But was this due solely to exercise? It’s hard to say. It’s possible that the women who exercised were also eating a low-fat diet or doing something else that was not identified by this study that helped to reduce the risk of a recurrence. In turn, the women who did not exercise at all may have been doing something else that increased their risk for recurrence.
Do these findings support the idea that a woman with an ER-positive tumor can substitute exercise for hormone therapy? It’s too early in the research on exercise to jump to that conclusion. You should make a decision on whether to use hormone therapy based on your risk of recurrence and what other treatments you had. Exercise can be thought of as an addition to other treatment, and it may be beneficial. But you shouldn’t count on it to do what an aromatase inhibitor or tamoxifen can.
Bottom-line: Adding just a small amount of exercise to your daily routine can pay-off in many ways. Weight-bearing exercise builds bone strength, which can reduce your risk for osteoporosis, while aerobic exercise builds cardiovascular strength, which can reduce your risk of heart disease. In addition, previous studies have found that women who exercise after their breast cancer diagnosis have a better quality of life than those who don’t. (Read related article here) And if your tumor is ER-positive, it may help keep your breast cancer from recurring.
References:
Chlebowski, RT, Blackburn, GL, Elashoff, RE, et al. Dietary Fat Reduction in Postmenopausal Women with Primary Breast Cancer: Phase III Women's Intervention Nutrition Study (WINS). Paper presented at the American Society of Clinical Oncologists (ASCO) 2005 Annual Meeting. Orlando FL, May 16, 2005.
Read Article.
Winters B, Mitchell D, et al. Dietary Patterns in Women Treated for Breast Cancer Who Successfully Reduced Fat Intake: The Women's Intervention Nutrition Study (WINS). JADA. 2004. 104:551-559.
Read Article.
Holmes, MD, Chen WY, et al. Physical Activity and Survival After Breast Cancer Diagnosis. JAMA. 2005. 293; 20: 2479-2486.
Read Article.
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