Unsupportive Data

A prospective cohort of 1982 women with breast cancer diagnosed between 1976 and 1990 were followed for 18 years. The cohort completed biennial questionnaires that included food frequency. The primary endpoint was time to all-cause mortality.6

Dietary fat intake was not associated with mortality, nor was there an association with red meat intake. High protein intake, however, was associated with reduced risk of mortality (relative risk high quintile vs low quintile, 0.65; 95% CI, 0.47-0.88).

In the multicenter Women’s Healthy Eating and Living (WHEL) trial, 3088 women with early-stage breast cancer aged 18 to 70 enrolled between 1995 and 2000 were randomly assigned to an intervention group or a control group. The intervention group received telephone counseling, cooking classes, and newsletters to encourage daily targets of vegetable, fruit, fiber, and fat intake, whereas the control group received print materials with the 5-A-Day dietary guidelines. The mean follow-up was 7.3 and the primary endpoint was an invasive breast cancer event or all-cause mortality.7

There was no significant difference in the rates of breast cancer events or all-cause mortality, though the women in the intervention group successfully maintained significantly higher vegetable (+65%), fruit (25%), and fiber (+30%) intake and lower fat intake (-13%; P < .001 for all).

Changes in dietary intake were confirmed using biomarkers such as plasma carotenoids, triacylglycerol, and high-density lipoprotein cholesterol. Baseline energy from fat was 28.5% and 28.7% in the intervention and control groups, respectively, and 28.9% and 32.4%, respectively at 72 months, indicating that although there were differences between the 2 groups, the intervention group did not lower their fat intake compared with baseline.

A secondary analysis of the WHEL trial that included 2967 women evaluated the effect of greater vegetable, fruit, and fiber intake and lower fat intake on the prognosis of women with and without hot flashes.8

Women without hot flashes had 31% fewer events than women without hot flashes in the intervention group (HR, 0.69; 95% CI, 0.51-0.93; P = .02) and in the control group (HR, 0.65; 95% CI, 0.49-0.85; P = .002), which suggests that the presence of hot flashes, but not diet, may be associated with breast cancer prognosis.

Conclusion

Differences in trial design, populations, and levels of energy intake from fat renders it difficult to achieve a definitive conclusion regarding the effect of a low-fat diet on breast cancer outcomes. Several trials demonstrate a decrease in all-cause mortality among women with breast cancer who adopt a low-fat diet. Yet other important factors, such as weight loss and the types of fats ingested, must be considered.

The data overall suggest that a low-fat diet with an increase in vegetable and fruit intake may lower the risk of all-cause mortality among women with breast cancer, but more studies are needed to provide patients with a definitive recommendation.

Reference

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  2. Blackburn GL, Wang KA. Dietary fat reduction and breast cancer outcome: results from the Women’s Intervention Nutrition Study (WINS). Am J Clin Nutr. 2007;86(3):s878-81.
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  8. Gold EB, Pierce JP, Natarajan L, et al. Dietary pattern influences breast cancer prognosis in women without hot flashes: the Women’s Healthy Eating and Living trial. J Clin Oncol. 2009;27:352-9. doi: 10.1200/JCO.2008.16.1067