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Dietary Intake and Prognosis after Breast Cancer
Abstract & Commentary
By Eileen C. West, MD, Director of Primary Care, Women's Health, Clinical Assistant Professor of Internal Medicine, University of Oklahoma School of Medicine, Oklahoma City. Dr. West reports no financial relationship to this field of study.
Synopsis: Patients with early breast cancer did not have fewer recurrences of cancer or improved mortality after eating a diet rich in vegetables and fruit and low in fat.
Source: Pierce JP, et al. JAMA. 2007;298(3):289-298.
Results of the Women's Healthy Eating and Living (WHEL) study were published in a recent issue of JAMA. In this multicenter, randomized controlled trial a total of 3088 women diagnosed with early-stage breast cancer (stage I-IIIa) within the previous four years were randomized to a diet rich in vegetables, fruit and fiber and low in fat, vs a regular diet. The two groups had no statistically significant differences in baseline demographics, tumor characteristics, dietary habits, or cancer treatment. The intervention group attended cooking classes, received 12 newsletters, and 18 telephone calls for counseling during the first year. The targets of the intervention group were on an intake of 5 vegetable servings plus 16 oz of vegetable juice, 3 fruit servings, 30 g of fiber and 15%-20% of calorie intake from fat. The control group was given print materials describing the "5-A-Day" dietary guidelines. The main outcome measures were invasive breast cancer event (recurrence or new primary) or death from any cause. After a mean of 7.3 years of follow-up, the authors found no differences in breast cancer events or all-cause mortality between women in the two groups.
Overall, the intervention group succeeded in eating 65% more vegetables, 25% more fruit, 30% more fiber, and 13% less fat than their colleagues ate in the comparison group, based on 24-hour telephone surveys. Investigators measured plasma carotenoid levels and confirmed the sustained change in dietary intake. In 7.3 years, 16.7% of the women in the intervention group developed an invasive breast cancer event, vs 16.9% in the comparison group. Similarly 10.1% of the women in the intervention group died, vs 10.3% in the comparison group. These numbers did not reach statistical significance at any point.
Finding any lifestyle elements which can improve outcomes of breast cancer is a worthy endeavor. Intuitively, it seems that healthy eating can and should improve outcomes of cancer survivorship. There are an estimated 2.4 million breast cancer survivors in the United States alone. Several published studies focused on breast cancer show mixed results. It does appear that a previous trial, the WINS trial, had marginally positive results that were based on lower levels of total energy intake and actual weight loss. Neither of those elements were present in this study. It can be noted that there was less success in the current study at achieving significant reduction in fat calories, and less weight loss in the groups of this trial.
As the authors point out, the WHEL study results are not intended to be applied to primary cancer prevention. Additionally, women who had undergone or were scheduled to undergo chemotherapy were not included, and there were relatively few minority women enrolled in the study.
In summary, although some dietary factors may ultimately prove to be important in reducing the risk for breast cancer recurrence, relatively small changes in vegetable, fruit, and fat intake alone did not make much difference.