In 2008, about 180 000 new cases of breast cancer were diagnosed in the United States, and 40 000 women died because of advanced breast cancer. Five-year survival for early stage breast cancer is 98% and drops to 89% for all stages together. There are an estimated 2 million breast cancer survivors in the United States today, and thus the implications of lifestyle modifications are enormous. Although diet and lifestyle have been associated and often implicated in the risk of developing breast cancer, there is very little known about their effect on breast cancer survival.
Understanding the consequences of diet and lifestyle on breast cancer survival is extremely important to breast cancer survivors who want to make appropriate choices to improve not only their life span but also the quality of life.
Only 2 published studies have looked at the relationship between diet after breast cancer diagnosis and long-term survival. Although the results are promising, it is too early to tell if these results will be confirmed over time. The Nurses' Sep o Oct 2009 Health Study examined diet after breast cancer diagnosis and its impact on survival. In this study, 1982 women with breast cancer were followed for an average of 13 years. Of that total, 1237 of the women did not develop metastatic disease. Women in this group who ate the largest amounts of poultry, total protein, and omega-3 fatty acids had a statistically significant lower risk of death compared to women who ate the least amounts of these foods and nutrients. Women who ate more fiber, fish, and vegetables also had a lower risk of death than women who ate less of these. The association of diet with survival was different for the 745 women who did develop metastasis. Women who ate the largest amounts of dairy products and had high levels of calcium in their diets had a significantly lower risk of death. In addition, women with metastasized tumors who ate more protein had a lower risk of death. No published studies have examined the effect of eating soy products on breast cancer survival.[70,71] Studies of women eating soy products daily have shown that soy-containing foods can act like estrogen and can cause cell proliferation in the breast. This could have a negative effect on breast cancer survival. Phytoestrogens in soy have also been reported to both oppose and complement the effects of tamoxifen in breast cancer cells. More study is needed in this area. At this time, it is a good idea for breast cancer survivors to avoid soy supplements and use soy-containing foods in moderation.
Some foods or nutrients were associated with as much as a 50% decrease in the risk of death. If these results prove to be correct, they could be quite important, as diet after diagnosis is something over which cancer survivors have control. It is important to recognize that these studies report associations and are not to be considered recommendations. The foods may just be representative of the women's life-style in general. Poultry products, such as chicken and turkey, are often viewed as healthier choices than red meat. Women who ate more poultry may also have been making other efforts toward a healthier lifestyle. Likewise, eating more hydrogenated oils may have been something done by the women who ate more processed baked foods (where these oils are found) and who were less concerned with healthy lifestyles.
Currently, it is unclear if specific diets before diagnosis affect breast cancer survival. Twelve studies have examined the effect of diet before breast cancer diagnosis on various aspects of survival. Four studies reported no association of survival with dietary fat consumption before diagnosis, but 5 studies reported that eating high levels of dietary fat was associated with a statistically significant increase in the risk of death. Some of these studies also examined the intake of vitamins A, C, and E from dietary food, not supplements, and showed differing results. Thus, no conclusions regarding the use of vitamins can be made at this time.
Although obesity at the time of diagnosis has been associated with decreased survival, it is unclear if weight gain after breast cancer diagnosis affects survival.[72,73] Weight gain is common in breast cancer patients after diagnosis and in 50% to 96% of all early stage breast cancer patients receiving chemotherapy. Two studies did not show any association between weight gain and an increased risk of cancer recurrence, but 2 other studies did report a possible association. Several studies have reported that weight gain is psychologically troubling and reduces the quality of life of breast cancer patients and thus negatively affects long-term outcome.[73,74]
The effect of low body weight at the time of diagnosis and weight loss following diagnosis has been studied less often. Three studies have reported poorer survival for women of low body weight at the time of diagnosis; 2 of these reports saw this effect only in women with advanced breast cancer. One study reported that the loss of 11 or more pounds in women of any body size was associated with poor survival.
The effect of exercise on breast cancer survival is not known.[75,76] It may improve the quality of life of breast cancer survivors, but no studies have directly examined how exercise after cancer diagnosis affects survival. An Australian study that followed 412 women with breast cancer for an average of 7 years showed no association of recreational exercise before diagnosis and survival.
Increasing physical activity, even if started later in life, reduces overall risk of developing breast cancer by 20% across women of all risk categories, including those considered to be high risk. Consistent physical activity is more important than how strenuous an activity is. Inducing a "negative energy balance"—where less energy is taken in than is spent—by eating a low-calorie diet or increasing exercise can decrease post-menopausal risk of breast cancer associated with obesity. Several studies have reported associations between exercise and improvements in the quality of life of breast cancer survivors, including improved mood, self-esteem, and sleep patterns and less nausea and fatigue. These studies differed greatly in their study design, so comparisons between the studies are difficult. The results, although currently early, show promise. A reasonable suggestion for exercise would be that recommended by the US Surgeon General, who recommends that everyone participate in moderate physical activity for at least 30 minutes 5 days a week.
Although smoking has been associated with numerous health problems, its effect on breast cancer survival is, as yet, not resolved. Well-conducted studies have demonstrated an association between smoking and an increase in the risk of death, but others show no association with the risk of death from breast cancer. Smokers may be at increased risk for the spread of cancer. Two studies have reported an increase in the metastasis of tumors from the breast to the lung in smokers. Survival of women who have stopped smoking has been examined in one study and found to be similar to that of women who never smoked.
Drinking alcoholic beverages is considered to be a risk factor for getting breast cancer. However, most but not all studies have reported no association between drinking alcoholic beverages and breast cancer survival.
It currently appears that group psychological therapy does not affect the survival of women with metastatic breast cancer. A recent well-designed study, along with 2 other studies, disagrees with an early study that found that group therapy increased the survival of women with metastatic cancer. Studies examining group psychological therapy for patients with other types of cancer have also reported mixed results. Yet, the support of fellow survivors and the encouragement to express concerns and feelings during group psychological therapy have been shown to have positive effects on breast cancer survivors' quality of life. Alternative medical practices have not been studied sufficiently to determine whether they can affect breast cancer survival.[82,83] Few epidemiological studies or clinical trials have examined alternative therapies for breast cancer survivors. More than 30% of the women diagnosed with breast cancer report using alternative treatments, including relaxation methods and spiritual practices; alternative medicines such as megavitamins, herbal medicines, and homeopathy; and healing therapies such as massage, chiropractic, acupuncture, and energy healing. More study is needed of these practices. To this end, the National Institutes of Health has established a National Center for Complementary and Alternative Medicine (https://nccam.nih.gov/) to fund and encourage the study of alternative medicine in various areas, including cancer treatment.
The preliminary studies looking at diet and lifestyle after breast cancer diagnosis are encouraging and support the concept that diet and lifestyle choices can make a difference for breast cancer survival, as well as help these women feel better. There is limited evidence on specific diet and lifestyle behaviors that women can use to increase survival, but living a healthy lifestyle is a sensible choice for breast cancer survivors.
Am J Lifestyle Med. 2009;3(5):337-348. © 2009 Sage Publications, Inc.
Cite this: Lifestyle Interventions in the Prevention and Treatment of Cancer - Medscape - Sep 01, 2009.